Three-phase half-bridge circuit, three-phase half-bridge circuit control method and charging module

Abstract

The invention provides a three-phase half-bridge circuit, a three-phase half-bridge circuit control method and a charging module. The three-phase half-bridge circuit comprises three half-bridge units, three LCL filtering units, two current sampling units and a voltage sampling unit. The input current waveform of the charging module can be flexibly adjusted by adopting the three-phase half-bridge topology, so that the output or absorption of reactive power is controlled, the high-performance reactive compensation function is realized, no direct electrical connection exists between the bus midpoint and the capacitor midpoint of the LCL filtering unit, and the three phases are mutually coupled to work, so that the working efficiency is improved. The inversion inductance current ripple frequency in the LCL filtering unit is twice of the switching frequency in the half-bridge unit, so that the inductance loss can be reduced, and the improvement of the electric energy conversion efficiency and the power density is facilitated; current and voltage signals are obtained through the sampling units, high-performance reactive compensation control can be realized through closed-loop calculation and switch control of the half-bridge unit, and a three-phase half-bridge only needs two current sampling units, so that the circuit design structure is effectively simplified.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a three-phase half-bridge circuit, a three-phase half-bridge circuit control method, and a charging module. Background Technology

[0002] In the field of electric vehicle charging, the large filtering inductance and capacitance of the charging module can cause the voltage and current phases to be inconsistent on the transmission line, resulting in reactive power loss and causing significant reactive power loss on the line, which in turn causes additional losses to the power grid.

[0003] Traditional charging modules, due to topological limitations, cannot compensate for this reactive power, or their compensation performance is poor, leading to problems such as high harmonic distortion. For example, the three-phase Vienna topology, which is widely used in traditional electric vehicle charging, cannot achieve high-performance reactive power compensation. It can only adjust the power factor (PF) during charging to meet the needs of simple reactive power regulation, and adjusting the PF can also lead to problems such as deterioration of iTHD. Summary of the Invention

[0004] The main purpose of this application is to provide a three-phase half-bridge circuit, a three-phase half-bridge circuit control method, and a charging module, which can at least solve the problems of poor reactive power compensation, large inductance loss, low conversion efficiency, and low power density in existing electric vehicle charging modules.

[0005] To achieve the above objectives, the first aspect of this application provides a three-phase half-bridge circuit, comprising: three half-bridge units, three LCL filter units, two current sampling units, and one voltage sampling unit; the first terminals of the three half-bridge units are all electrically connected to the positive terminal of the DC bus, the second terminals of the three half-bridge units are all electrically connected to the negative terminal of the DC bus, the midpoints of the three half-bridge units are respectively electrically connected to the corresponding LCL filter units, the frequency of the inverter inductor current in the LCL filter unit is twice the frequency of the switching transistor in the half-bridge unit; the first current sampling unit is electrically connected to any one of the LCL filter units, the second current sampling unit is electrically connected to any one of the remaining two LCL filter units, and the voltage sampling unit is electrically connected to each of the three LCL filter units.

[0006] The second aspect of this application provides a three-phase half-bridge circuit control method, applied to the three-phase half-bridge circuit as described in the first aspect of this application. The method includes: receiving current sampled in real time by a current sampling unit and voltage sampled in real time by a voltage sampling unit; performing calculations on the current, the voltage, and a preset reference value of reactive current to be compensated to generate a drive signal and transmitting it to the switching transistor in the half-bridge unit; wherein the drive signal is used to adjust the operating state of the switching transistor to adjust the amplitude and phase of the AC current, thereby performing reactive power compensation and active power transmission.

[0007] A third aspect of this application provides an electric vehicle charging module, including a three-phase half-bridge circuit as described in the first aspect of this application, the three-phase half-bridge circuit being used to execute the three-phase half-bridge circuit control method of the second aspect.

[0008] As described above, the three-phase half-bridge circuit used in this application can flexibly adjust the input current waveform to control the output or absorption of reactive power, thereby achieving high-performance reactive power compensation and active power transmission. Furthermore, there is no direct electrical connection between the bus midpoint and the LCL filter unit; the three phases are coupled together. During reactive power compensation, the inductor current in the LCL filter unit is affected by the two-phase half-bridge unit, resulting in an inductor current ripple frequency twice the switching frequency in the half-bridge unit. This reduces inductor losses and improves energy conversion efficiency and power density. Current and voltage signals are acquired through current and voltage sampling units. These signals are then calculated against a preset reference value for the reactive current to be compensated, adjusting the drive control signal of the switching transistors in the half-bridge unit. This enables reactive power compensation control and active power transmission. Moreover, based on this three-phase half-bridge circuit structure, the three-phase current can be acquired through only two current sampling units, simplifying the circuit design. Attached Figure Description

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 This is a schematic diagram of a three-phase Vienna topology in related technologies;

[0011] Figure 2 This is a schematic diagram of a three-phase half-bridge circuit according to an embodiment of this application;

[0012] Figure 3 This is a circuit schematic diagram of a three-phase half-bridge circuit according to an embodiment of this application;

[0013] Figure 4 This is a schematic diagram of a three-phase half-bridge topology with a neutral line in related technologies;

[0014] Figure 5 This is a diagram showing the phase correspondence between the inductor current waveform and the drive in a three-phase half-bridge topology with a neutral line in related technologies.

[0015] Figure 6 This is a diagram showing the phase correspondence between the inductor current waveform and the drive in a three-phase half-bridge circuit according to an embodiment of this application.

[0016] Figure 7 This is a basic flowchart of a three-phase half-bridge circuit control method according to an embodiment of this application;

[0017] Figure 8 This is a schematic diagram of a current and voltage signal processing flow according to an embodiment of this application. Detailed Implementation

[0018] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In related technologies, electric vehicle charging modules mostly adopt the traditional three-phase Vienna topology, and its structure is as follows: Figure 1 As shown, this topology, due to the presence of unidirectional diodes D1 to D6, cannot control bidirectional current flow, thus failing to achieve high-performance reactive power compensation regulation. To regulate reactive power, this topology can only adjust part of the current phase by controlling the conduction time of MOSFETs Q1 to Q6 during charging. However, to maintain sufficient charging power, this control method requires changing the MOSFET conduction time under different AC voltage phases, followed by filtering with a large filter to achieve the effect of changing the current phase. This inevitably leads to a deterioration in iTHD and makes reactive power compensation impossible when no DC power is output (such as in standby mode or when not charging to compensate for the reactive power of other devices). Therefore, this application provides a three-phase half-bridge circuit.

[0020] like Figure 2The diagram shows a three-phase half-bridge circuit according to an embodiment of this application. The three-phase half-bridge circuit includes: three half-bridge units 100, three LCL filter units 200, two current sampling units 300, and one voltage sampling unit 400. The first terminals of the three half-bridge units 100 are all electrically connected to the positive terminal of the DC bus, and the second terminals of the three half-bridge units 100 are all electrically connected to the negative terminal of the DC bus. The midpoints of the three half-bridge units 100 are electrically connected to the corresponding LCL filter units 200. The first current sampling unit 300 is electrically connected to any one of the LCL filter units 200, the second current sampling unit 300 is electrically connected to any one of the remaining two LCL filter units 200, and the voltage sampling unit 400 is electrically connected to each of the three LCL filter units 200. The frequency of the inverter inductor current in the LCL filter unit is twice the frequency of the switching transistor in the half-bridge unit.

[0021] Compared to the three-phase Vienna topology in related technologies, the three-phase half-bridge circuit used in this embodiment can flexibly adjust the input current waveform to control the output or absorption of reactive power, thereby achieving high-performance reactive power compensation. Furthermore, there is no direct electrical connection between the bus midpoint and the LCL filter unit 200; the three phases are coupled together. During reactive power compensation, the inductor current in the LCL filter unit 200 is affected by the two-phase half-bridge unit 100, resulting in an inductor current ripple frequency twice the switching frequency in the half-bridge unit 100. This reduces inductor losses and improves energy conversion efficiency and power density. Current and voltage signals are acquired through the current sampling unit 300 and voltage sampling unit 400, respectively. The drive control signals of the switching transistors in the half-bridge unit 100 are adjusted based on these signals, thereby achieving reactive power compensation control. Moreover, based on this three-phase half-bridge circuit structure, the acquisition of three-phase current can be achieved through two current sampling units 300, simplifying the circuit design.

[0022] like Figure 3 The diagram shown is a circuit schematic of a three-phase half-bridge circuit according to an embodiment of this application. Please refer to [link / reference]. Figure 2 and Figure 3 The LCL filter unit 200 includes an inverter inductor (L1 / L2 / L3), an inverter capacitor (C1 / C2 / C3), and a filter inductor (L4 / L5 / L6). One end of the inverter inductor (L1 / L2 / L3) is electrically connected to the midpoint of the corresponding half-bridge unit 100. The other end of the inverter inductor (L1 / L2 / L3) is electrically connected to one end of the inverter capacitor (C1 / C2 / C3) and one end of the filter inductor (L4 / L5 / L6), respectively. The other end of the filter inductor (L4 / L5 / L6) is electrically connected to the voltage sampling unit 400. The other end of the inverter capacitor (C1 / C2 / C3) is connected to the floating midpoint. The current sampling unit is connected to the middle of any two phase filter inductors and inverter inductors of the LCL filter unit.

[0023] Further, please see Figure 2 and Figure 3 The current sampling unit 300 includes a first shunt (RS1 / RS3) and a second shunt (RS2 / RS4). The first shunt (RS1 / RS3) is electrically connected to the other end of the inverter inductor (L1 / L2 / L3) and one end of the inverter capacitor (C1 / C2 / C3), respectively. The second shunt (RS2 / RS4) is electrically connected to one end of the inverter capacitor (C1 / C2 / C3) and one end of the filter inductor (L4 / L5 / L6), respectively. The shunts can also be replaced by current measuring devices such as Hall effect devices.

[0024] Further, please see Figure 2 and Figure 3 The voltage sampling unit 400 includes three voltage divider resistor units, each including a first resistor (R1 / R3 / R5) and a second resistor (R2 / R4 / R6). One end of the first resistor (R1 / R3 / R5) is electrically connected to the other end of the filter inductor (L4 / L5 / L6), and the second resistor (R2 / R4 / R6) is electrically connected to the other end of the first resistor (R1 / R3 / R5) and the virtual midpoint, respectively.

[0025] Specifically, in this embodiment, each phase half-bridge of the three-phase half-bridge circuit includes two switching transistors connected in series. The switching transistors can be power switching devices such as MOSFETs, IGBTs, and BJTs. Taking MOSFETs as an example, in each phase half-bridge, the drain of the upper transistor is connected to the positive bus, the source is connected to the drain of the lower transistor, and the source of the lower transistor is connected to the negative bus. The midpoint of each phase bridge arm is connected to one end of the inverter inductors (i.e., L1, L2, L3) of the front-stage LCL filter unit 200. The other ends of two inverter inductors (L1, L3) are connected to one end of the current sampling shunt (RS1, RS3), the other end of the current sampling shunt is connected to one end of the inverter capacitors (C1, C3), the other end of the other inverter inductor (i.e., L2) is directly connected to one end of the inverter capacitor C2, and the other ends of the three inverter capacitors (C1, C2, C3) are connected to the same floating midpoint. One end of the current sampling shunt RS1 and one end of the inverter capacitor C1 are simultaneously connected to one end of the previous stage's current sampling shunt RS2. The other end of the current sampling shunt RS2 is connected to one end of the filter inductor L4, and the other end of the filter inductor L4 is connected to the input port. One end of the current sampling shunt RS3 and one end of the inverter capacitor C3 are simultaneously connected to one end of the previous stage's current sampling shunt RS4. The other end of the current sampling shunt RS4 is connected to one end of the filter inductor L6, and the other end of the filter inductor L6 is connected to the input port. The other end of the inverter inductor L2 and one end of the inverter capacitor C2 are directly connected to the filter inductor L5, and the other end of the filter inductor L5 is connected to the input port. The voltage sampling unit 400 has one voltage divider resistor unit in each phase, and the ends of the three voltage divider resistor units are connected to the same floating virtual midpoint.

[0026] It should be noted that the three-phase half-bridge topology can provide high-performance reactive power compensation, but for a three-phase half-bridge topology with a neutral line, its structure is as follows: Figure 4 As shown, due to the presence of the neutral line N, the three phases are completely decoupled into three independent single-phase circuits. That is, each of the three phase circuits operates independently, and the frequency of its inductor current is equal to the switching frequency of the MOSFET. The phase correspondence between its inductor current waveform and the drive is as follows: Figure 5 As shown, this results in a large inductor current ripple, high losses, and low power conversion efficiency, leading to low power density in the product.

[0027] In this embodiment, the three-phase half-bridge circuit lacks a neutral line, and the three phases are coupled together. During reactive power compensation, the current flows from the positive bus, through the upper half-bridge arm of one phase (e.g., MOSFET Q1), through the inverter inductor L1 and inverter capacitor C1 of that phase, then through the inverter capacitor (e.g., capacitor C2) of another phase, to the inverter inductor L2, and finally through the lower half-bridge arm MOSFET Q4 of that phase before returning to the negative bus. Thus, the inductor current ripple is affected by the MOSFETs of two phases, and the inductor current ripple frequency is twice the MOSFET switching frequency. The corresponding phase relationship between the inductor current waveform and the drive is shown in the diagram below. Figure 6 As shown, the peak-to-peak value of the inductor ripple is reduced under this topology, and the inductor loss is decreased, effectively improving the product's power conversion efficiency and power density. Furthermore, the two current sampling units 300 and the voltage sampling unit 400 respectively acquire current and voltage signals. Since there is no direct electrical connection between the bus midpoint (i.e., point O) of the three-phase half-bridge circuit and the midpoint of the preceding inverter capacitors (C1 to C3), the preceding LCL filter unit 200 can use an asymmetrical current sampling method, that is, only sampling the current before and after two phase inverter capacitors (i.e., the current through the four shunts), and then calculating the inverter capacitor current of that phase through the current difference before and after the same phase. This inverter capacitor current can be used for virtual impedance compensation and control; and by the three-phase vector sum being 0, the inverter inductor current and inverter capacitor current of the third phase (excluding the two phases mentioned above) can be calculated. In addition, since the three-phase half-bridge topology has no neutral line, the input voltages U1, U2, and U3 are sampled by voltage division relative to the virtual neutral point, and the line voltage can be obtained by subtracting each pair of samples. By acquiring these current and voltage signals, the operating mode of the three-phase half-bridge circuit can be controlled. The operating modes include charging mode (PF is constant at 1), PF adjustment mode (adjusted according to the grid's PF control and scheduling requirements for electrical equipment), pure reactive power compensation mode (no active power is output, used as a reactive power compensator), and hybrid output mode (can compensate or offset its own reactive power while outputting active power for charging).

[0028] The three-phase half-bridge circuit provided in this application embodiment can flexibly adjust the input current waveform to control the output or absorption of reactive power, thereby achieving high-performance reactive power compensation. Furthermore, there is no direct electrical connection between the bus midpoint and the LCL filter unit; the three phases are coupled together. During reactive power compensation, the inductor current in the LCL filter unit is affected by the two-phase half-bridge unit, causing the inductor current ripple frequency to be twice the switching frequency in the half-bridge unit. This reduces inductor losses and improves energy conversion efficiency and power density. Current and voltage signals are acquired through current and voltage sampling units, and the drive control signals of the switching transistors in the half-bridge unit are adjusted based on these signals, thereby achieving reactive power compensation control. Moreover, based on this three-phase half-bridge circuit structure, the three-phase current can be acquired through only two current sampling units, simplifying the circuit design.

[0029] This application also provides a three-phase half-bridge circuit control method, applied to the aforementioned three-phase half-bridge circuit, such as... Figure 7 The diagram shown is a basic flowchart of a three-phase half-bridge circuit control method provided in this embodiment. The method includes:

[0030] Step 701: Receive the current sampled in real time by the current sampling unit and the voltage sampled in real time by the voltage sampling unit;

[0031] Step 702: Calculate the current, voltage, and preset reference value of reactive current to be compensated, generate a drive signal, and transmit it to the switching transistor in the half-bridge unit.

[0032] Specifically, in this embodiment, two current sampling units can sample the current of the two-phase circuit in real time, and a voltage sampling unit can sample the input voltage of the three-phase circuit in real time. By acquiring these current and voltage signals, and by acquiring the preset reactive current value to be compensated, the required drive signal can be determined after calculation. Based on the drive signal, the operating state of the switching transistors in the half-bridge unit is adjusted, that is, the on and off states of the switching transistors are adjusted, thereby realizing the amplitude and phase adjustment of the AC current, and performing reactive power compensation and active power transmission. It should be understood that the three-phase half-bridge circuit can convert DC power to AC power or AC power to DC power. Each phase circuit includes two switching devices (such as MOSFETs or IGBTs), each corresponding to one half-cycle of the phase current. During operation, the phase and amplitude of the input current can be adjusted by controlling the on and off states of these switches.

[0033] In some embodiments of this example, before generating a drive signal by calculating the current, voltage, and preset reference value of reactive current to be compensated, the method further includes: obtaining a preset power quality index; wherein the power quality index includes a target power factor, reactive power, or active power; and determining the reference value of reactive current to be compensated based on the power quality index.

[0034] Specifically, in this embodiment, the reactive current value to be compensated can be determined based on the actual power quality requirements. The power quality index can be the required target power factor, reactive power, or active power. The power factor is an important indicator that measures the relationship between actual power and apparent power in an AC circuit. The power factor value is between 0 and 1; a higher value indicates higher energy utilization efficiency. When determining the compensation requirement, the current power factor can be measured first to determine the actual reactive power. Then, the target reactive power is calculated based on the target power factor. By comparing the difference between the current actual reactive power and the target reactive power, the required reactive power compensation can be determined, and a reactive current reference value can be obtained after conversion.

[0035] In other embodiments of this example, calculations are performed on the current, voltage, and a preset reference value for the reactive current to be compensated to generate a drive signal, including: calculating a third current based on a first current and a second current; wherein the first current is the current sampled by the second shunt in the first current sampling unit, and the second current is the current sampled by the second shunt in the second current sampling unit; subtracting the fourth current and the fifth current to obtain a sixth current; wherein the fourth current is the current sampled by the first shunt in the first current sampling unit, and the fifth current is the current sampled by the first shunt in the second current sampling unit; and performing calculations on the first to sixth currents, the voltage, and the preset reference value for the reactive current to be compensated to generate a drive signal.

[0036] Specifically, in this embodiment, although only two current sampling units perform current sampling, the current of the third phase can be calculated from the acquired two-phase currents. Since the three-phase vector sum is 0, the input current of the first phase and the input current of the second phase can be subtracted from 0 to obtain the input current of the third phase. Figure 2 Taking a three-phase half-bridge circuit as an example, in this embodiment, the first current is the current sampled by the second shunt in the first current sampling unit, which is also the input current of phase U1, I(in1) = I(rs2), and the second current is the current sampled by the second shunt in the second current sampling unit, which is also the input current of phase U3, I(in3) = I(rs4). The input current of phase U2, I(in2), can be obtained by the formula I(in2) = 0 - I(in1) - I(in3). Similarly, the inverter inductance of the first phase can be subtracted from 0. The inverter inductor current of the third phase is obtained from the current and the inverter inductor current of the second phase. In this embodiment, the fourth current is the current collected by the first shunt in the first current sampling unit, which is the inverter inductor current of phase U1, I(L1) = I(rs1). The fifth current is the current collected by the first shunt in the second current sampling unit, which is the inverter inductor current of phase U3, I(L3) = I(rs3). The inverter inductor current of phase U2, I(L2), is obtained by the formula I(L2) = 0 - I(L1) - I(L3). Based on these input currents (i.e., the first current I(in1), the second current I(in3), and the third current I(in2)), the inverter inductor currents (i.e., the fourth current I(L1), the fifth current I(L3), and the sixth current I(L2)), the input voltage collected by the voltage sampling unit, and the preset reference value of the reactive current to be compensated, the drive signal can be determined.

[0037] Furthermore, in some other embodiments of this example, calculations are performed on the first to sixth currents, voltage, and a preset reference value for the reactive current to be compensated to generate a drive signal. This includes: subtracting the first current and the fourth current to obtain a seventh current; the seventh current is the current of the inverter capacitor in the LCL filter unit connected to the first current sampling unit; subtracting the third current and the fifth current to obtain an eighth current; the eighth current is the current of the inverter capacitor in the LCL filter unit connected to the second current sampling unit; subtracting the second current and the sixth current to obtain a ninth current; the eighth current is the current of the inverter capacitor in the LCL filter unit that is not connected to a current sampling unit; and performing calculations on the first to ninth currents, voltage, and the preset reference value for the reactive current to be compensated to generate a drive signal.

[0038] Specifically, in this embodiment, after obtaining the inverter inductor current and input current of each phase, the current on the inverter capacitor of that phase can be calculated by subtracting the two currents. For example, the current on the inverter capacitor C1 of phase U1 (i.e., the seventh current) is I(c1) = I(in1) - I(L1), where I(in1) is the first current, i.e., the input current of phase U1, and I(L1) is the fourth current, i.e., the inverter inductor current of phase U1; the current on the inverter capacitor C2 of phase U2... The eighth current (i.e., I(c2) = I(in2) - I(L2), where I(in2) is the third current, i.e., the input current of phase U2, and I(L2) is the sixth current, i.e., the inverter inductor current of phase U2. The current on the inverter capacitor C3 of phase U3 (i.e., the ninth current) is I(c3) = I(in3) - I(L3), where I(in3) is the second current, i.e., the input current of phase U3, and I(L3) is the fifth current, i.e., the inverter inductor current of phase U3. Since the LCL filter unit does not directly add actual damping, but by calculating the inverter capacitor current of each phase, it can be used for virtual impedance compensation, which improves the stability of product control and reduces cost and device losses. Finally, a drive signal is generated based on these input currents (i.e., the first current I(in1), the second current I(in3), and the third current I(in2)), the inverter inductor currents (i.e., the fourth current I(L1), the fifth current I(L3), and the sixth current I(L2)), the inverter capacitor currents (i.e., the seventh current I(c1), the eighth current I(c2), and the ninth current I(c3)), the input voltage of each phase, and the preset reference value of the reactive current to be compensated.

[0039] Furthermore, in some embodiments of this example, calculations are performed on the first to ninth currents, voltages, and a preset reference value for the reactive current to be compensated to generate a drive signal. This includes: performing a dq transformation on the first to ninth currents and voltages to obtain active current components, reactive current components, active voltage components, and reactive voltage components; calculating the active DC voltage and reactive DC voltage based on the active current components, reactive current components, active voltage components, reactive voltage components, and the preset reference value for the reactive current to be compensated; performing an inverse dq transformation on the active DC voltage and reactive DC voltage; and modulating the inverse dq transformed active DC voltage and reactive DC voltage to obtain the drive signal.

[0040] Specifically, in this embodiment, such as Figure 8 As shown in the schematic diagram of the signal processing flow, by performing dq transformation on the voltage and current signals, the DC small signals, namely the active component id / ud and the reactive component iq / uq, can be obtained. Combined with the reference value of the reactive current to be compensated iq*, the virtual impedance compensation value calculated from the inverter capacitor current, and the corresponding PI controller processing, the required DC small signals, namely the active DC voltage Ud and the reactive DC voltage Uq, can be obtained. After inverse dq transformation, Ud and Uq are further modulated to be converted into switching transistor control drive signals, realizing the adjustment of AC current amplitude and phase, and performing reactive power compensation and active power transmission.

[0041] The three-phase half-bridge circuit control method provided in this application receives real-time current from a current sampling unit and real-time voltage from a voltage sampling unit. Based on the current, voltage, and a preset reference value for the reactive current to be compensated, a drive signal is generated and transmitted to the switching transistors in the half-bridge unit. By acquiring the current of two phases and the input voltage of the three-phase circuit, the current of the other phase can be calculated based on the acquired current. The current on the inverter capacitor is determined based on the calculated current, enabling virtual impedance compensation. Based on these currents, voltages, virtual impedance compensation values, and the preset reference value for the reactive current to be compensated, a drive signal is determined. Based on this drive signal, the switching transistors of the three-phase half-bridge are controlled to achieve AC current amplitude and phase adjustment, providing high-performance reactive power compensation and active power charging for the product.

[0042] This application also provides an electric vehicle charging module, which includes the above-mentioned three-phase half-bridge circuit.

[0043] It should be noted that the various embodiments in this application are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0044] It should also be noted that, in this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified. The terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] The above description of the disclosed embodiments enables those skilled in the art to implement or use the content of this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined in this application may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A three-phase half-bridge circuit, characterized in that, include: Three half-bridge units, three LCL filter units, two current sampling units, and one voltage sampling unit; The first end of each of the three half-bridge units is electrically connected to the positive terminal of the DC bus, and the second end of each of the three half-bridge units is electrically connected to the negative terminal of the DC bus. The midpoint of each of the three half-bridge units is electrically connected to the corresponding LCL filter unit. The frequency of the inverter inductor current in the LCL filter unit is twice the frequency of the switching transistor in the half-bridge unit. The first current sampling unit is electrically connected to any one of the LCL filter units, the second current sampling unit is electrically connected to any one of the remaining two LCL filter units, and the voltage sampling unit is electrically connected to each of the three LCL filter units.

2. The three-phase half-bridge circuit according to claim 1, characterized in that, The LCL filter unit includes an inverter inductor, an inverter capacitor, and a filter inductor. One end of the inverter inductor is electrically connected to the midpoint of the corresponding half-bridge unit. The other end of the inverter inductor is electrically connected to one end of the inverter capacitor and one end of the filter inductor. The other end of the filter inductor is electrically connected to the voltage sampling unit. The other end of the inverter capacitor is connected to the floating midpoint. The current sampling unit is connected to the middle of any two phase filter inductors and the inverter inductor of the LCL filter unit.

3. The three-phase half-bridge circuit according to claim 2, characterized in that, The current sampling unit includes a first shunt and a second shunt; The first shunt is electrically connected to the other end of the inverter inductor and one end of the inverter capacitor, respectively, and the second shunt is electrically connected to one end of the inverter capacitor and one end of the filter inductor, respectively.

4. The three-phase half-bridge circuit according to claim 2, characterized in that, The voltage sampling unit includes three voltage divider resistor units, each including a first resistor and a second resistor. One end of the first resistor is electrically connected to the other end of the filter inductor, and the second resistor is electrically connected to the other end of the first resistor and the virtual midpoint, respectively.

5. A three-phase half-bridge circuit control method, characterized in that, The method, using the three-phase half-bridge circuit as described in any one of claims 1 to 4, comprises: It receives the current sampled in real time by the current sampling unit and the voltage sampled in real time by the voltage sampling unit. The current, the voltage, and the preset reference value of the reactive current to be compensated are calculated to generate a drive signal, which is then transmitted to the switching transistor in the half-bridge unit. The drive signal is used to adjust the operating state of the switching transistor to adjust the amplitude and phase of the AC current, thereby performing reactive power compensation and active power transmission.

6. The three-phase half-bridge circuit control method according to claim 5, characterized in that, Before generating the drive signal by calculating the current, the voltage, and the preset reference value of the reactive current to be compensated, the process further includes: Obtain preset power quality indicators; wherein, power quality indicators include any one of the following: target power factor, target reactive power, and target active power; The reference value of the reactive current to be compensated is determined based on the power quality indicators.

7. The three-phase half-bridge circuit control method according to claim 5, characterized in that, The step of calculating the current, the voltage, and the preset reference value of the reactive current to be compensated to generate a drive signal includes: The third current is calculated based on the first current and the second current; wherein the first current is the current sampled by the second shunt in the first current sampling unit, and the second current is the current sampled by the second shunt in the second current sampling unit; The sixth current is calculated based on the fourth current and the fifth current; wherein the fourth current is the current sampled by the first shunt in the first current sampling unit, and the fifth current is the current sampled by the first shunt in the second current sampling unit. The first to sixth currents, the voltage, and the preset reference value of the reactive current to be compensated are calculated to generate a drive signal.

8. The three-phase half-bridge circuit control method according to claim 7, characterized in that, The step of calculating the first to sixth currents, the voltage, and a preset reference value for the reactive current to be compensated to generate a drive signal includes: The difference between the first current and the fourth current is used to obtain the seventh current; the seventh current is the current of the inverter capacitor in the LCL filter unit connected to the first current sampling unit. The difference between the third current and the fifth current is used to obtain the eighth current; the eighth current is the current of the inverter capacitor in the LCL filter unit connected to the second current sampling unit. The difference between the second current and the sixth current is used to obtain the ninth current; the eighth current is the current of the inverter capacitor in the LCL filter unit that is not connected to the current sampling unit. The first to ninth currents, the voltage, and the preset reference value of the reactive current to be compensated are calculated to generate a drive signal.

9. The three-phase half-bridge circuit control method according to claim 8, characterized in that, The step of calculating the first to ninth currents, the voltage, and a preset reference value for the reactive current to be compensated to generate a drive signal includes: The first current to the ninth current and the voltage are subjected to dq transformation to obtain active current component, reactive current component, active voltage component and reactive voltage component; Based on the active current component, reactive current component, active voltage component, reactive voltage component, and preset reference value of reactive current to be compensated, calculate the active DC voltage and reactive DC voltage. The active DC voltage and reactive DC voltage are subjected to inverse dq transformation, and the active DC voltage and reactive DC voltage after inverse dq transformation are modulated to obtain a drive signal.

10. An electric vehicle charging module, characterized in that, Includes the three-phase half-bridge circuit as described in any one of claims 1 to 4.

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