A soft switch design and control method for multi-port DC / DC converters

Abstract

The present invention discloses a soft switch design and control method applicable to a multi-port DC / DC converter, which is applicable to a soft switch control mode with any number of source and load ports. By designing the transformer ratio and modulating the duty ratio of the source port and the load port, a soft switch condition in which the voltages between the ports are matched is constructed, which can realize the ZVS opening of the switch tubes of all ports, reduce the switching loss of the converter, and improve the efficiency of the converter. At the same time, the control mode of the present invention can reduce the current peak value of the AC side of the H bridge of each port, reduce the conduction loss of the converter at this time, improve the efficiency of the converter, and facilitate the design and selection of transformers and devices.

Description

Technical Field

[0001] The invention belongs to the field of AC / DC hybrid power distribution network system, in particular to a soft switch design and control method suitable for a multi-port DC / DC converter. Background Art

[0002] With the access of a large number of new energy sources, energy storage equipment, and new loads such as electric vehicles in the power system, the power system is showing a trend of AC / DC hybrid connection, and a high degree of power electronics is showing in all links of network-source-load-storage. As the core power conversion structure in the power electronic transformer, the multi-port isolated DC / DC converter plays the role of isolation-level voltage conversion, power transmission and electrical isolation. The multi-port DC / DC converter provides an energy interaction point and energy flow path for multiple sources and multiple loads in the AC / DC hybrid power distribution system, and its efficient operation is of great significance to the AC / DC hybrid power distribution system.

[0003] In a multi-port DC / DC converter, since energy can be transferred between any two ports, the ports are coupled with each other, which is not conducive to the optimization control analysis and solution of the multi-port DC / DC converter soft switch. Moreover, in the current optimization control of the multi-port DC / DC converter soft switch, the existing soft switch optimization control method is complex and has the problem of local optimal solution, and it is impossible to achieve the soft switching of all port switch tubes within the full power range. If the soft switching of the multi-port DC / DC converter can be achieved within the full power range, the switching loss of the switch tube can be reduced and the efficiency of the converter can be improved. Summary of the invention

[0004] In view of the defects existing in the prior art, the present invention provides a soft switching design and control method suitable for a multi-port DC / DC converter. Within the full power range, soft switching of the switch tube at each port can be realized to reduce the switching loss of the converter; it can also effectively reduce the current peak of each port, reduce the loss at the time of switch tube action, and improve the efficiency of the converter.

[0005] A soft switch design and control method for a multi-port DC / DC converter, wherein the n-port module multi-active bridge converter comprises: n ports, including a relay port r, 1 to k (excluding port r) source ports, j to n (excluding port r) load ports. Each port is configured as follows: the relay port r is composed of a single-phase H-bridge module, a DC capacitor and a high-frequency transformer (the high-frequency transformer of the relay port can be selected not to be added).

[0006] The source port is composed of a single-phase H-bridge module, a DC capacitor, a high-frequency transformer and a high-frequency inductor (the high-frequency inductor can be replaced by the transformer leakage inductance).

[0007] The load port is composed of a single-phase H-bridge module, a DC capacitor, a high-frequency transformer and a high-frequency inductor (the high-frequency inductor can be replaced by the transformer leakage inductance).

[0008] The DC side of the source port single-phase H-bridge module is connected in parallel with the DC capacitor and then connected to the power supply, and the AC side is connected to the primary side of the high-frequency transformer through a high-frequency inductor; the DC side of the load port single-phase H-bridge module is connected in parallel with the DC capacitor and then connected to the load, and the AC side is connected to the primary side of the high-frequency transformer through a high-frequency inductor; the DC side of the relay port single-phase H-bridge module is only connected in parallel with the DC capacitor, and the AC side is directly connected to the primary side of the high-frequency transformer. The secondary sides of the high-frequency transformers of each port are connected according to the corresponding relationship to form a high-frequency AC bus, realizing mutual power transmission between the ports of the n-port module multi-active bridge converter.

[0009] In the n-port module multi-active bridge converter, V x Indicates the DC side voltage of the single-phase H-bridge module at port x (x=1…n). x Indicates the AC side voltage of the single-phase H-bridge module at port x (x=1…n). Lx Indicates the AC side current of the single-phase H-bridge module at port x (x = 1…n), C x Represents the DC capacitance of the DC side of the single-phase H-bridge module at port x (x=1…n). R represents the load connected to the DC side of the single-phase H-bridge module. T x Represents a double-winding high-frequency transformer at port x (x = 1...n). N xp and N xs Respectively represent the number of turns of the primary and secondary windings of the high-frequency transformer at port x (x = 1…n). x represents the duty cycle control signal of port x (x=1…n), Represents the external phase angle control signal of port x (x=1...n).

[0010] The steps include:

[0011] Design the high-frequency transformer ratio of the source port and the load port;

[0012] Design the high-frequency inductance Lx of the source port and the load port and the converter switching frequency fs;

[0013] Given the trunk port duty cycle control signal δr, the trunk port duty cycle control signal δ r Set to 1;

[0014] Given the source port and the load port duty cycle control signal δx;

[0015] Given the external phase shift control signal of the relay port Shift the phase angle control signal outside the relay port Set to 0;

[0016] Given the source port and the load port external phase angle control signal

[0017] Generate a relay port switch tube drive signal;

[0018] Generate source port and load port switch tube driving signals.

[0019] Based on the above scheme, the high-frequency transformer ratio of the designed source port and the load port is specifically:

[0020] Select a suitable voltage as the voltage reference value V 参考值 (If the relay port is directly connected to the high-frequency AC bus without passing through a high-frequency transformer, the DC side voltage of the relay port V r As the reference voltage V 参考值 ), according to the minimum value V of the DC side voltage at the source port and the DC side voltage at the load port that may fluctuate x_min Design the transformer ratio of each port as shown in the formula. xp and N xs They respectively represent the number of primary and secondary winding turns of the high-frequency transformer at port x (x=1…n).

[0021]

[0022] Based on the above scheme, the high-frequency inductance Lx of the source port and the load port and the converter switching frequency fs are specifically designed as follows:

[0023] According to the rated transmission power P of each port N , select the appropriate port inductance and converter switching frequency, as shown in the formula. r ' refers to the voltage value of the DC side voltage of the relay port converted to port x (x = 1 ... n, x ≠ r), V x Refers to the DC side voltage value of port x (x=1…n, x≠r), Refers to the external phase shift angle of each port. Taking into account the actual stray parameters and the requirement of 20% overload, the maximum external phase shift angle can be designed to be 0.3π.

[0024]

[0025] Based on the above solution, the given source port and load port duty cycle control signal δx is specifically:

[0026] DC voltage V at port x x Real-time sampling is performed and the minimum voltage value V set by the port is x_min By comparison, the duty cycle control signal δ of port x is obtained. x, as shown in the formula.

[0027]

[0028] On the basis of the above scheme, the external phase shift angle control signal of the relay port is set is 0 and serves as a reference for the external phase shift angles of other ports.

[0029] Based on the above scheme, the voltage reference V x_ref and DC side voltage V x The voltage error obtained by subtracting the voltage error; the controller outputs the external phase angle control signal of port x Among them, the port x external shift phase angle is defined as the phase difference between the midpoint of the square wave of the relay port r and the port x full-bridge inverter.

[0030] Based on the above scheme, the relay port switch tube S is generated according to the duty cycle of the relay port and the external phase shift angle control signal. r1 ~S r4 The pulse drive signal is used as a reference for other ports.

[0031] On the basis of the above scheme,

[0032] For the control of the source port, a source port is responsible for controlling the relay port voltage V r For the control of the source port, a source port is responsible for controlling the relay port voltage V r Stability, collect the DC side voltage V of the relay port and the reference value V ref The controller makes a difference and obtains the external phase angle control signal of the source port.

[0033] Other source ports control the output current of their ports by comparing the DC side current I of the source port with the reference value I ref The external phase angle control signal of other source ports is obtained through the controller.

[0034] The external phase shift angle control signal of the source port is ahead of the external phase shift angle control signal of the relay port;

[0035] For the control of the load port, according to the different types of connected loads, voltage or current closed-loop control is performed on it, the output voltage or output current of the port is collected, and the external phase angle control signal of the load port is obtained through the output of the controller;

[0036] The load port external phase shift angle control signal lags behind the relay port external phase shift angle control signal;

[0037] According to the duty cycle control signal of the source port and the load port, under the joint action of the external phase angle control signal and the voltage duty cycle control signal, the port x switch tube S is generated. x1 ~Sx4 Pulse drive signal.

[0038] Based on the above solution, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0039] Based on the above solution, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0040] Beneficial effects of the present invention:

[0041] The soft switch design and control method of the multi-port DC / DC converter disclosed in the present invention utilizes the design of the high-frequency transformer ratio of each port and the given duty cycle control signal to construct a soft switch condition in which the voltages between ports are matched, and can realize the zero voltage turn-on of the switch tubes of each port within the full power range, reduce the turn-on loss of the switch tubes, and effectively reduce the current peak of each port, improve the efficiency of the multi-port DC / DC converter, and facilitate the use of the multi-port DC / DC converter in any source-load system and improve its comprehensive benefits. On the other hand, the present invention can realize the power decoupling of the source-load port by using the relay port without considering the mode of power transmission between ports, and only needs to design and give the control signal for each port, which is simple to control, high in feasibility and good in effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The present invention has the following accompanying drawings:

[0043] Figure 1 1 is a schematic diagram of the circuit structure of a multi-port DC / DC converter according to an embodiment of the present invention;

[0044] Figure 2 It is the AC voltage waveform measured by the single-phase H-bridge module of the relay port and the load port when lightly loaded in an embodiment of the present invention;

[0045] Figure 3 The single-phase H-bridge module AC voltage waveform of the relay port and the load port when overloaded in the embodiment of the present invention;

[0046] Figure 4 is a closed-loop control block diagram of an embodiment of the present invention;

[0047] Figure 5 This is the circuit structure of the first specific embodiment of the present invention;

[0048] Figure 6 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the existing single phase shift control method of the first specific embodiment of the present invention;

[0049] Figure 7 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the soft switch optimization control implemented in the first specific embodiment of the present invention;

[0050] Figure 8 is the circuit structure of the second specific embodiment of the present invention;

[0051] Fig. 9 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the existing single phase shift control method of the second specific embodiment of the present invention;

[0052] Fig.10 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the soft switch optimization control of the second specific embodiment of the present invention;

[0053] Fig.11 is the circuit structure of the third specific embodiment of the present invention;

[0054] Fig.12 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the existing single phase shift control method of the third specific embodiment of the present invention;

[0055] Fig.13 It is a waveform diagram of the inductor current of each port and the AC voltage measured by the H-bridge module under the soft switch optimization control of the third specific embodiment of the present invention;

[0056] Fig.14 It is an implementation flow chart of the present invention. DETAILED DESCRIPTION

[0057] To make the objects, advantages and features of the present invention more apparent, the following Figure 1-14 The present invention is further described in detail with specific embodiments 1-3.

[0058] The soft switch control method of a multi-port DC / DC converter disclosed in the present invention is applicable to a multi-port DC / DC converter with any number of source and load ports, wherein the multi-port DC / DC converter comprises a relay port, a plurality of source ports and a plurality of load ports. The relay port is composed of a single-phase H-bridge module, a DC capacitor and a high-frequency transformer (the high-frequency transformer of the relay port can be selected not to be added). The source port or the load port is composed of a single-phase H-bridge module, a DC capacitor, a high-frequency transformer and a high-frequency inductor (the high-frequency inductor can be replaced by the transformer leakage inductance). The DC side of the single-phase H-bridge module of the relay port is only connected to the DC capacitor, and the AC side is connected through the high-frequency transformer. The DC side of the single-phase H-bridge module of the source port (load port) is connected to the power supply (load) in parallel with the DC capacitor, and the AC side is connected to the primary side of the high-frequency transformer through the high-frequency inductor. The secondary sides of the high-frequency transformers of each port are connected according to the corresponding relationship, and two common high-frequency AC busbars are formed. Different ports are connected together through the high-frequency AC busbar to realize the mutual transmission of energy.

[0059] The soft switch control method of the multi-port DC / DC converter disclosed in the present invention, the single-phase H-bridge module AC voltage waveform of the relay port and any load port is as follows: Figure 2 and 3 shown. Figure 2 and 3 The AC voltage waveform of the single-phase H-bridge module at the load port lags behind that of the relay port. When the external phase shift angle between the relay port and the load port is very small, it is a light load condition when the formula is satisfied. At this time, the AC voltage waveform of the single-phase H-bridge module between the relay port and any load port is as follows: Figure 2 When the external phase shift angle of the relay port and the load port increases to meet the formula shown in the formula, it is a heavy load condition. At this time, the AC voltage waveform of the single-phase H-bridge module between the relay port and any load port is as follows: Figure 3 As shown. The single-phase H-bridge module AC voltage waveforms of the relay port and the source port are similar, except that the single-phase H-bridge module AC voltage waveform of the source port is ahead of the relay port. The power emitted by the source port can also be expressed by and. When the external phase shift angle between the source port and the relay port satisfies the formula, it means that the power emitted by the source port is small. When the external phase shift angle between the source port and the relay port satisfies the formula, it means that the power emitted by the source port is large.

[0060]

[0061]

[0062] The soft switch design and control method of the multi-port DC / DC converter disclosed in the present invention comprises the following steps:

[0063] Step 1: Design the high-frequency transformer ratio of each port. Select a suitable voltage as the voltage reference value V参考值 (If the relay port is directly connected to the high-frequency AC bus without passing through a high-frequency transformer, the DC side voltage of the relay port V r As the reference voltage V 参考值 ), according to the minimum value V of the DC side voltage at the source port and the DC side voltage at the load port that may fluctuate x_min Design the transformer ratio of each port as shown. xp and N xs They respectively represent the number of primary and secondary winding turns of the high-frequency transformer at port x (x=1…n).

[0064]

[0065] Step 2: High-frequency inductance L of port x x (x=1…n, x≠r, i.e., the high-frequency inductance of the source port and the load port) and the converter switching frequency f s According to the rated transmission power P of each port N , select the appropriate port inductance and converter switching frequency, as shown in the formula. r ' refers to the voltage value of the DC side voltage of the relay port converted to port x (x = 1 ... n, x ≠ r), V x Refers to the DC side voltage value of port x (x=1…n, x≠r), Refers to the external phase shift angle of each port. Taking into account the actual stray parameters and the requirement of 20% overload, the maximum external phase shift angle can be designed to be 0.3π.

[0066]

[0067] Step 3: Relay port duty cycle control signal δ r Given, the relay port duty cycle control signal δ r Set to 1.

[0068] Step 4: Port x (x = 1 ... n, x ≠ r, refers to the source port and the load port) duty cycle control signal δ x Given. The DC voltage V at port x x Real-time sampling is performed and the minimum voltage value V set by the port is x_min By comparison, the duty cycle control signal δ of port x is obtained. x , as shown in the formula.

[0069]

[0070] Step 5: External phase shift control signal of relay port Set the external phase angle control signal of the relay port. is 0 and serves as a reference for the external phase shift angles of other ports.

[0071] Step 6: Port x (x = 1 ... n, x ≠ r, refers to the source port and the load port) external phase angle control signal The voltage reference V through port x x_ref and DC side voltage V x The voltage error obtained by subtraction is output by the controller as a port x external phase shift control signal, wherein the port x external phase shift is defined as the phase difference between the midpoint of the square wave of the relay port r and the port x full-bridge inverter.

[0072] Step 7: Generate the relay port switch tube drive signal. Generate the relay port switch tube S according to the duty cycle and external phase angle control signal of the relay port obtained in step 3 and step 5. r1 ~S r4 The pulse drive signal is used as a reference for other ports.

[0073] Step 8: Generation of switch tube drive signal at port x (x=1…n, x≠r, referring to source port and load port). Fig.14 The closed-loop control block diagram of each port is shown. For the control of the source port, a source port is responsible for controlling the voltage V of the relay port. r The other source ports control the output current of their ports, which is equivalent to controlling the power emitted by the source ports. For example, port 1 in the figure is responsible for maintaining the relay port voltage V r The external phase angle control signal of port 1 is obtained through step 4, and the external phase angle control signal of the source port is ahead of the reference signal. The other source ports (port k) are equivalent to current sources, and the external phase angle control signal of port k is obtained by controlling the output current. Similarly, the control signal is ahead of the reference signal. For the control of the load port, voltage or current closed-loop control is performed on it according to the type of load connected, and the output voltage or output current of the acquisition port is obtained through step 4. The external phase angle control signal of the load port lags behind the reference signal. Combined with the duty cycle control signals of the source port and the load port obtained in step 3, under the joint action of the external phase angle control signal and the voltage duty cycle control signal, the port x switch tube S is generated. x1 ~S x4 Pulse drive signal.

[0074] The following is further described by specific examples 1-3.

[0075] The present invention is applicable to a multi-port DC / DC converter circuit with any number of source and load ports. The circuit structure includes n+1 high-frequency transformers, n+1 single-phase H-bridge modules, and n+1 DC side DC capacitors C 1 …C n and C r and n-port equivalent inductance L 1 …Ln The output voltage of the AC side of each port single-phase H-bridge module is represented by u, and the AC current of the AC side is represented by i L , the DC side voltage is represented by V.

[0076] Embodiment 1, as Figure 5 As shown:

[0077] In a multi-source and multi-load system, in order to verify the feasibility and effectiveness of the present invention, this embodiment takes a 5-port DC / DC converter as an example, wherein port 1 is a relay port, the AC side of the single-phase H-bridge module is directly connected to the high-frequency AC bus through a high-frequency transformer, there is no resistance on the DC side, and its steady-state voltage is set to 200V; port 2 is a source port, its single-phase H-bridge DC side is connected to a voltage source, the voltage fluctuation is 200V~300V, the AC side is directly connected to the high-frequency AC bus through a high-frequency transformer, and this port is responsible for maintaining the stability of the DC side voltage of the relay port; port 3 is also a source port, its single-phase H-bridge DC side is connected to a voltage source, the voltage fluctuation is 200V~300V, the AC side is directly connected to the high-frequency AC bus through a high-frequency transformer, and the DC side current is closed-loop controlled to control its output power to 1250W; ports 4 and 5 are both load ports, connected to a 100Ω resistor, and the DC side voltages of ports 4 and 5 are 200V~300V respectively when they are in steady-state operation.

[0078] Assuming the voltage reference value V 参考值 The minimum DC side voltage that the source port and the load port (port 2 to 5) can operate is 200V. According to step 1, the high-frequency transformer ratio of each port is 1:1. Then, according to the rated transmission power between ports of 5kW, the converter switching frequency is selected as 10kHz, and the inductance of each port is calculated as 150μH according to step 2.

[0079] According to step 4, the duty cycle control signals of the source port and the load port are obtained by the ratio of the actual value of the DC side voltage of the single-phase H-bridge module at the source port and the load port to the minimum value. In combination with step 4 and step 5, the external phase angle control signal of each port is given. In Example 1, a certain steady-state operating point is used for demonstration, and the simulation results are shown as follows: Figure 4-Figure 5 shown.

[0080] The output voltage and current waveforms of the AC side of the single-phase H-bridge module at each port using traditional single phase shift modulation are as follows: Figure 4 As shown. The switch tube S of port 1 11 and S 14 When turned on, the AC side current i L1 >0, so the switch tube S of port 1 11 and S 14 ZVS cannot be turned on, and S 12 and S 13Respectively with S 11 and S 14 In the same bridge arm, ZVS cannot be achieved. 21 and S 24 When turned on, the AC side current i L2 <0, so the switch tube S of port 1 21 and S 24 ZVS can be turned on, and S 22 and S 23 Respectively with S 21 and S 24 In the same bridge arm, ZVS can also be achieved. By analyzing the soft switching of the switch tubes at ports 3, 4, and 5 in the same way, it can be seen that all the switch tubes at ports 3, 4, and 5 can achieve ZVS. In short, when the traditional single phase shift modulation method is used, the switch tube at port 1 cannot achieve ZVS conduction, resulting in high switching loss and reduced efficiency during converter operation.

[0081] Figure 5 The voltage and current waveforms of the AC side of the single-phase H-bridge modules of each port when the control method of the present invention is adopted, and the steady-state operating point of the multi-port DC / DC converter is consistent with that when the traditional single-phase phase-shift modulation is adopted. At this time, the DC side input voltage of the single-phase H-bridge module of port 2 is 300V, and its duty cycle control signal is 2 / 3 according to step 2; the DC side input voltage of the single-phase H-bridge module of port 3 is 250V, and its duty cycle control signal is 0.8 according to step 2; the DC side output voltage of the single-phase H-bridge module of port 4 is 280V, and its duty cycle control signal is 1 / 14 according to step 2; the DC side output voltage of the single-phase H-bridge module of port 5 is 280V, and its duty cycle control signal is 2 / 3 according to step 2. Figure 5 In the example, the switch S of port 1 11 and S 14 When turned on, the AC side current i L1 =0, so the switch tube S of port 1 11 and S 14 At the critical ZVS turn-on, S 12 and S 13 Respectively with S 11 and S 14 In the same bridge arm, critical ZVS can also be achieved. 21 When turned on, the AC side current i L2 <0, so the switch tube S of port 2 21 ZVS can be achieved, and the switch tube S 23 With S 21 In the same bridge arm, ZVS can also be achieved. 22 When turned on, the AC side current i L2 >0, so the switch tube S of port 222 ZVS can be achieved, and the switch tube S 24 With S 22 In the same bridge arm, ZVS can also be achieved. In the same way, the soft switching of the switch tubes of ports 3, 4 and 5 is analyzed, and it can be seen that all the switch tubes of ports 3, 4 and 5 can achieve ZVS. In short, when the control method of the present invention is used, each port of the multi-port DC / DC converter can achieve ZVS, which reduces the switching loss of the converter and improves the efficiency.

[0082] contrast Figure 4 and Figure 5 It can be seen that the control method of the present invention can significantly reduce the peak current of the AC side of the single-phase H-bridge module at each port. Reducing the port current peak has a great impact on the selection of devices and the design of transformers. At the same time, it can also reduce the switching loss of the switch tube and the core loss of the transformer at this moment.

[0083] Embodiment 2, as Figure 8 As shown:

[0084] In a one-source multi-load system, in order to verify the feasibility and effectiveness of the present invention, this embodiment takes a 4-port DC / DC converter as an example. In a one-source multi-load system, the function of the source port can be replaced by a relay port, that is, port 1 is used as a relay port and has the function of a source port. The DC side of the single-phase H-bridge can be connected to a voltage source with a voltage value of 200V, and the AC side is directly connected to the primary side of the high-frequency transformer without a high-frequency inductor (or directly connected to the high-frequency AC bus). Ports 2, 3, and 4 are all used as load ports. The AC side of the single-phase H-bridge is directly connected to the primary side of the high-frequency transformer through a high-frequency inductor, and the DC side is connected to a resistor. The DC side voltages of ports 2, 3, and 4 are set to be 200V to 300V respectively when the ports 2, 3, and 4 are in steady-state operation.

[0085] Assuming the voltage reference value V 参考值 The minimum DC side voltage that the source port (port 2 to 4) can operate is 200V, and the high-frequency transformer ratio of each port is 1:1 according to step 1. Then, according to the rated transmission power between ports of 5kW, the converter switching frequency is selected as 10kHz, and the inductance of each port is calculated as 150μH according to step 2.

[0086] According to step 4, the duty cycle control signals of the source port and the load port are obtained by the ratio of the actual value of the DC side voltage of the single-phase H-bridge module at the load port to the minimum value. In combination with step 4 and step 5, the external phase angle control signal of each port is given. In Example 2, a certain steady-state operating point is used for demonstration, and the simulation results are shown as follows: Figure 9-10 shown.

[0087] When the load ports are all operating under light load conditions, the output voltage and current waveforms of the AC side of the single-phase H-bridge module at each port using traditional single phase shift modulation are as follows: Fig. 9 As shown. The switch tube S of port 1 11 and S 14 When turned on, the AC side current i L1 >0, so the switch tube S of port 1 11 and S 14 ZVS cannot be turned on, and S 12 and S 13 Respectively with S 11 and S 14 In the same bridge arm, ZVS cannot be achieved. 21 and S 24 When turned on, the AC side current i L1 <0, so the switch tube S of port 2 21 and S 24 ZVS can be turned on, and S 22 and S 23 Respectively with S 21 and S 24 In short, when the traditional single phase shift modulation method is used, the switch tube of port 1 cannot achieve ZVS conduction, which makes the switching loss of the converter higher and the efficiency lower.

[0088] Fig.10 The voltage and current waveforms of the AC side of the single-phase H-bridge modules of each port when the control method of the present invention is adopted, and the steady-state operating point of the multi-port DC / DC converter is consistent with that when the traditional single phase shift modulation is adopted. At this time, the DC side output voltage of the single-phase H-bridge module of port 2 is 300V, and its duty cycle control signal is 2 / 3 according to step 2; the DC side output voltage of the single-phase H-bridge module of port 3 is 260V, and its duty cycle control signal is 1 / 13 according to step 2; the DC side output voltage of the single-phase H-bridge module of port 4 is 280V, and its duty cycle control signal is 1 / 14 according to step 2. Fig.10 The switch tube S of the middle port 1 11 and S 14 When turned on, the AC side current i L1 =0, so the switch tube S of port 1 11 and S 14 At the critical ZVS turn-on, S 12 and S 13 Respectively with S 11 and S 14 In the same bridge arm, critical ZVS can also be achieved. 21 When turned on, the AC side current i L2 <0, so the switch tube S of port 2 21ZVS can be achieved, and the switch tube S 23 With S 21 In the same bridge arm, ZVS can also be achieved. 22 When turned on, the AC side current i L2 >0, so the switch tube S of port 2 22 ZVS can be achieved, and the switch tube S 24 With S 22 In the same bridge arm, ZVS can also be achieved. By analyzing the soft switching of the switch tubes of ports 3 and 4 in the same way, it can be seen that all the switch tubes of ports 3 and 4 can achieve ZVS. In short, when the control method of the present invention is used, each port of the multi-port DC / DC converter can achieve ZVS, which reduces the switching loss of the converter and improves efficiency.

[0089] contrast Fig. 9 and Fig.10 It can be seen that the control method of the present invention can significantly reduce the peak current of the AC side of the single-phase H-bridge module at each port. Reducing the port current peak has a great impact on the selection of devices and the design of transformers. At the same time, it can also reduce the switching loss of the switch tube and the core loss of the transformer at this moment.

[0090] Embodiment 3, as Fig.11 As shown:

[0091] In a one-source multi-load system, in order to verify the feasibility and effectiveness of the present invention, this embodiment takes a 4-port DC / DC converter as an example. In a multi-source one-load system, the function of the load port can be replaced by a relay port, that is, port 4 is used as a relay port and has the function of a load port. The single-phase H-bridge DC side can be connected to the load, and its steady-state voltage reference value is 200V. The AC side is directly connected to the primary side of the high-frequency transformer without a high-frequency inductor (or directly connected to the high-frequency AC bus). Ports 1, 2, and 3 are all used as source ports. The single-phase H-bridge AC side is directly connected to the primary side of the high-frequency transformer through a high-frequency inductor, and the DC side is connected to a resistor. The DC side input voltage is set to 200V to 300V when ports 1, 2, and 3 are in steady-state operation.

[0092] Assuming the voltage reference value V 参考值 The minimum DC side voltage that the source port (port 1 to 3) can operate is 200V. The high-frequency transformer ratio of each port is 1:1 according to step 1. Then, according to the rated transmission power between ports of 5kW, the converter switching frequency is selected as 10kHz, and the inductance of each port is calculated as 150μH according to step 2.

[0093] According to step 4, the duty cycle control signals of the source port and the load port are obtained by the ratio of the actual value of the DC side voltage of the single-phase H-bridge module at the source port to the minimum value. In combination with step 4 and step 5, the external phase angle control signal of each port is given. In Example 3, a certain steady-state operating point is used for demonstration, and the simulation results are shown as follows: Figure 12-13 shown.

[0094] When the load port is operating under light load conditions, the output voltage and current waveforms of the AC side of the single-phase H-bridge module at each port using traditional single phase shift modulation are as follows: Fig.12 As shown. The switch tube S of port 4 41 and S 44 When turned on, the AC side current i L4 >0, so the switch tube S of port 4 41 and S 44 ZVS cannot be turned on, and S 42 and S 43 Respectively with S 41 and S 44 In the same bridge arm, ZVS cannot be achieved. 11 and S 14 When turned on, the AC side current i L1 <0, so the switch tube S of port 1 11 and S 14 ZVS can be turned on, and S 12 and S 13 Respectively with S 11 and S 14 In short, when the traditional single phase shift modulation method is used, the switch tube of port 4 cannot achieve ZVS conduction, which makes the switching loss higher and the efficiency lower when the converter is running.

[0095] Fig.13 The voltage and current waveforms of the AC side of the single-phase H-bridge modules of each port when the control method of the present invention is adopted, and the steady-state operating point of the multi-port DC / DC converter is consistent with that when the traditional single phase shift modulation is adopted. At this time, the DC side input voltage of the single-phase H-bridge module of port 1 is 300V, and its duty cycle control signal is 2 / 3 according to step 2; the DC side input voltage of the single-phase H-bridge module of port 2 is 270V, and its duty cycle control signal is 2 / 27 according to step 2; the DC side output voltage of the single-phase H-bridge module of port 3 is 240V, and its duty cycle control signal is 1 / 14 according to step 2. Fig.13 In the example, the switch S of port 4 41 and S 44 When turned on, the AC side current i L4 =0, so the switch tube S of port 4 41 and S 44 At the critical ZVS turn-on, S42 and S 43 Respectively with S 41 and S 44 In the same bridge arm, critical ZVS can also be achieved. 11 When turned on, the AC side current i L1 <0, so the switch tube S of port 1 11 ZVS can be achieved, and the switch tube S 13 With S 11 In the same bridge arm, ZVS can also be achieved. 12 When turned on, the AC side current i L1 >0, so the switch tube S of port 1 12 ZVS can be achieved, and the switch tube S 14 With S 12 In the same bridge arm, ZVS can also be achieved. By analyzing the soft switching of the switch tubes of ports 2 and 3 in the same way, it can be seen that all the switch tubes of ports 2 and 3 can achieve ZVS. In short, when the control method of the present invention is used, each port of the multi-port DC / DC converter can achieve ZVS, which reduces the switching loss of the converter and improves efficiency.

[0096] contrast Fig.12 and Fig.13 It can be seen that the control method of the present invention can significantly reduce the peak current of the AC side of the single-phase H-bridge module at each port. Reducing the port current peak has a great impact on the selection of devices and the design of transformers. At the same time, it can also reduce the switching loss of the switch tube and the core loss of the transformer at this moment.

[0097] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the essence and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The scope of patent protection of the present invention should be limited by the claims.

[0098] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A soft switch design and control method for a multi-port DC / DC converter, which is suitable for a multi-port isolated DC / DC converter having a relay port r, 1 to k source ports, and j to n load ports; wherein: The source port and the load port do not include a relay port r; It is characterized by comprising the following steps: Design the high-frequency transformer ratio of the source port and the load port; Design the high-frequency inductance Lx of the source port and the load port and the converter switching frequency fs; Given a relay port duty cycle control signal , the relay port duty cycle control signal Set to 1; Given the source port and load port duty cycle control signal ; Given the relay port external phase shift angle control signal , shift the phase angle control signal of the relay port externally Set to 0; Given the source port and the load port external phase angle control signal ; Generate a relay port switch tube drive signal; Generate source port and load port switch tube drive signals; Generate a pulse drive signal for the switch tube of the relay port according to the duty cycle of the relay port and the external phase shift angle control signal, and use it as a reference for other ports; The relay port is composed of a single-phase H-bridge module, a DC capacitor and a high-frequency transformer; the DC side of the single-phase H-bridge module of the relay port is only connected in parallel with the DC capacitor, and the AC side is directly connected to the primary side of the high-frequency transformer; For the control of the source port, a source port is responsible for controlling the stability of the relay port voltage Vr, collecting the difference between the DC side voltage V of the relay port and the reference value Vref, and obtaining the external phase angle control signal of the source port through the controller; The other source ports control the output current of their ports, collect the DC side current I of the source port and make a difference with the reference value Iref, and obtain the external phase angle control signal of the other source ports through the controller; The external phase shift angle control signal of the source port is ahead of the external phase shift angle control signal of the relay port; For the control of the load port, according to the different types of connected loads, voltage or current closed-loop control is performed on it, the output voltage or output current of the port is collected, and the external phase angle control signal of the load port is obtained through the output of the controller; The load port external phase shift angle control signal lags behind the relay port external phase shift angle control signal; Under the joint action of the external phase-shift angle control signal and the voltage duty cycle control signal, a pulse drive signal of the port x switch tube is generated.

2. A soft switch design and control method for a multi-port DC / DC converter according to claim 1, characterized in that: The high-frequency transformer ratio of the designed source port and load port is specifically: Selecting a voltage reference ; According to the minimum value of the DC voltage fluctuation at each port , design the transformer ratio of each port, as shown in formula (1); ; If the relay port is directly connected to the high-frequency AC bus without passing through a high-frequency transformer, the DC side voltage V r As a reference voltage , design the high frequency transformer ratio of source port and load port; in, N xp and N xs Respectively represent ports x The number of turns of the primary and secondary windings of the high-frequency transformer, x =1…n.

3. A soft switch design and control method for a multi-port DC / DC converter according to claim 1, characterized in that: The high-frequency inductance Lx of the source port and the load port and the converter switching frequency fs are specifically designed as follows: According to the rated transmission power P of each port N , select the port inductance and converter switching frequency, as shown in formula (2): ; Among them, V r 'Refers to the DC side voltage of the relay port calculated to the port x The voltage value, V x Refers to the port x DC side voltage value, Refers to the external phase angle of each port, x =1…n, x ≠r.

4. The soft switch design and control method for a multi-port DC / DC converter according to claim 1, characterized in that: The given source port and load port duty cycle control signal Specifically: Port x DC side voltage V x Perform real-time sampling; Compare the sampled value with the minimum voltage set for the port Compare and find the port x Duty cycle control signal , as shown in formula (3): 。 5. The soft switch design and control method for a multi-port DC / DC converter according to claim 1, characterized in that: Set the external phase angle control signal of the relay port is 0 and serves as a reference for the external phase shift angles of other ports.

6. A soft switch design and control method for a multi-port DC / DC converter according to claim 1, characterized in that: Via Port x Voltage reference V x_ref and DC side voltage V x The voltage error obtained by subtraction; Output via controller as port x The external phase angle control signal ; Among them, port x The external phase angle is defined as the relay port r and the port x The phase difference of the square wave midpoint of the full-bridge inverter.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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