A DC bias suppression method for renewable energy access-type grid-connected grid-connected grids based on operating condition classification.

Abstract

This invention discloses a DC bias suppression method for renewable energy access-type TAB converters based on operating condition mode classification, belonging to the fields of DC converters and power electronics. This method suppresses transient DC bias generated when the operating condition of a single output port of an isolated three-port converter changes. In implementation, the suppression time of transient DC bias is greatly accelerated by operating all three ports simultaneously. Due to the coupling relationship between the first port and the other two ports, a port compensation scheme is designed when the first port is in operation. By modeling the transient DC bias under the full-cycle, full-phase-shift state, real-time suppression of transient DC bias in isolated three-port converters can be achieved under conditions such as arbitrary operating condition switching and operating condition changes at any time during the working cycle.

Description

Technical Field

[0001] This invention belongs to the field of DC converters and power electronics, specifically relating to a DC bias suppression method for new energy access type TAB (isolated three-port converter) based on operating mode classification. Background Technology

[0002] As my country's transportation infrastructure construction continues to advance, the need for coordinated development among railways, power grids, and new energy systems is becoming increasingly prominent.

[0003] Due to the rapid development of power electronics technology, replacing traditional traction transformers with power electronic converters has become an important trend. Some scholars have proposed flexible AC traction power supply systems using power electronic converters. The AC-DC-AC structure has advantages such as flexible voltage regulation and high degree of freedom in power control, making it an important technical path for building flexible traction power supply systems. It can achieve controllable and adjustable voltage across the entire traction network, completely eliminate phase separation, and has an intermediate DC link in its power conversion process, laying a good foundation for the integration of distributed new energy sources.

[0004] Utilizing new energy sources will facilitate the green development of railways, while energy storage systems can store new energy sources and regenerative braking energy from trains, improving system energy utilization. Currently, new energy sources and energy storage systems are mainly connected to the rail transit traction power supply system through their respective corresponding converters, increasing the system's size and weight, and requiring additional communication devices, thus reducing system reliability. Isolated three-port converters can simultaneously connect multiple new energy source input ports, increasing converter power density and making them suitable for high-power applications.

[0005] Under single-phase-shift control, when the operating conditions of an isolated three-port converter change, the port phase shift will abruptly change, leading to transient DC bias. Transient DC bias not only increases the current stress on the switching devices, jeopardizing their safe operation, but may also cause transformer magnetic saturation, affecting the normal operation of the converter. Existing transient DC bias suppression strategies mainly involve inserting a transition period. These strategies are computationally simple but slow, typically requiring a full switching cycle to achieve the desired suppression effect. Summary of the Invention

[0006] To address the aforementioned shortcomings in existing technologies, the new energy access-type TAB DC bias suppression method based on operating mode classification provided by this invention solves the problem that existing transient DC bias suppression strategies are simple to calculate but slow in suppression speed, thereby improving the transient DC bias suppression speed.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention is as follows: a DC bias suppression method for new energy access-type TAB based on operating condition mode classification, used to suppress the transient DC bias generated when the operating condition of a single port of an isolated three-port converter changes, comprising the following steps: S100. Obtain the port voltage of the second / third port in the isolated three-port converter, compare it with the corresponding reference voltage to obtain the voltage error signal, and then determine the shift between the switching transistor drive signals of the first port and the second / third port before and after the operating condition change. S200. Perform transient DC calculations on the phase shift ratio before and after the operating condition jump to obtain the first volt-second difference value caused by the phase shift at the second / third port. S300: Sample and obtain the operating condition switching time of the second / third port, and perform offset calculation by combining the shift ratio before and after the operating condition switching to obtain the second volt-second difference value of the second / third port caused by the switching time; S400. Based on the first volt-second difference value and the second volt-second difference value, combined with the working mode and working status when the current working condition changes, determine the bias suppression strategy and bias suppression time of the second / third port under the corresponding working condition. S500: Based on the bias suppression strategy and bias suppression time, determine the actual output phase shift angle between the drive signals of the first port and the second / third port switching transistors, and generate the corresponding switching signal after single-phase-shift PWM modulation, thereby realizing the transient DC bias suppression of the isolated three-port converter TAB.

[0008] The beneficial effects of this invention are as follows: 1. This invention proposes a transient DC bias suppression strategy for an isolated three-port converter. Compared with the traditional suppression method that inserts a transition period, it can complete transient DC bias compensation more quickly after the operating condition changes, significantly shorten the bias suppression time, and improve the converter's response speed under dynamic operating conditions such as load changes, power command changes, and power flow direction switching.

[0009] 2. This invention does not require fixing the transient DC bias processing at the start of the switching cycle. Instead, it combines the actual operating condition transition time to calculate the volt-second difference caused by the sudden change in the shift ratio and the switching time, and determines the compensation time based on the total volt-second difference, thereby improving the real-time performance, accuracy and control flexibility of bias suppression.

[0010] 3. Based on the different shift ratios, power transmission direction, and transition time, this invention divides the operating state of the isolated three-port converter into modes, and adopts corresponding compensation or maintenance processing methods for different operating modes and states. This can avoid the problems of miscompensation, overcompensation, or compensation failure caused by a single fixed compensation logic, and improve the applicability of the strategy under multiple operating conditions.

[0011] 4. This invention does not require changing the main circuit topology or adding extra hardware. It can achieve transient DC bias suppression simply by adjusting the switching signal. It has the advantages of simple implementation, low engineering application cost, and easy integration.

[0012] 5. This invention designs a collaborative compensation strategy for coupled ports, which can suppress transient DC bias of the switching port while offsetting the coupling effect of the compensation action on other normally operating ports, ensuring the stability of voltage, current and power transmission in non-switching ports, reducing current stress on switching devices and transformer magnetic bias risk, and improving the operational reliability of isolated three-port converters in scenarios such as new energy access, energy storage collaboration and traction power supply. Attached Figure Description

[0013] Figure 1 The flowchart of the new energy access-type TAB DC bias suppression method based on operating condition mode classification provided by the present invention is shown.

[0014] Figure 2 The diagram shows the structure of the isolated three-port bidirectional DC / DC converter provided by this invention.

[0015] Figure 3 The waveform of the isolated three-port converter provided by this invention.

[0016] Figure 4 The schematic waveform of transient DC bias generated during the change of operating conditions provided by the present invention.

[0017] Figure 5 The equivalent volt-second product waveform of the isolated three-port converter provided by this invention.

[0018] Figure 6 The basic principle diagram of transient DC bias suppression provided by the present invention.

[0019] Figure 7 The schematic diagram of the suppression principle of mode ① working state 1 provided by the present invention.

[0020] Figure 8 The schematic diagram of the maintenance state suppression principle provided by the present invention is shown in section ①.

[0021] Figure 9 The schematic diagram of the suppression principle of mode ① working state 2 provided by the present invention.

[0022] Figure 10 The principle diagram for mode ② suppression provided by the present invention.

[0023] Figure 11 The principle diagram for mode ③ suppression provided by the present invention.

[0024] Figure 12The schematic diagram of the working state 1 and the suppression principle of the maintenance state provided by the present invention.

[0025] Figure 13 The schematic diagram of the suppression principle of mode ④ working state 2 provided by the present invention.

[0026] Figure 14 The schematic diagram of mode ⑤ suppression principle provided by the present invention.

[0027] Figure 15 The principle diagram for mode ⑥ suppression provided by the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0029] This invention provides a DC bias suppression method for new energy access-type TAB converters based on operating mode classification. By operating three ports simultaneously, the suppression time of transient DC bias is greatly accelerated. Based on the coupling relationship between the first port and the second and third ports, a port compensation scheme is designed when the first port is in operation. By modeling the transient DC bias under the full-cycle full-phase shift state, real-time suppression of transient DC bias of isolated three-port converters is realized under conditions such as arbitrary operating mode switching and operating mode jumps at any time during the working cycle.

[0030] refer to Figure 1 A DC bias suppression method for renewable energy access-type TAB converters based on operating condition classification is used to suppress transient DC bias generated when the operating condition of a single port of an isolated three-port converter changes. The method includes the following steps: S100. Obtain the port voltage of the second / third port in the isolated three-port converter, compare it with the corresponding reference voltage to obtain the voltage error signal, and then determine the shift between the switching transistor drive signals of the first port and the second / third port before and after the operating condition change. S200. Perform transient DC calculations on the phase shift ratio before and after the operating condition jump to obtain the first volt-second difference value caused by the phase shift at the second / third port. S300: Sample and obtain the operating condition switching time of the second / third port, and perform offset calculation by combining the shift ratio before and after the operating condition switching to obtain the second volt-second difference value of the second / third port caused by the switching time; S400. Based on the first volt-second difference value and the second volt-second difference value, combined with the working mode and working status when the current working condition changes, determine the bias suppression strategy and bias suppression time of the second / third port under the corresponding working condition. S500: Based on the bias suppression strategy and bias suppression time, determine the actual output phase shift angle between the drive signals of the first port and the second / third port switching transistors, and generate the corresponding switching signal after single-phase-shift PWM modulation, thereby realizing the transient DC bias suppression of the isolated three-port converter TAB.

[0031] In Embodiment 1 of the present invention, the structure of the isolated three-port converter is as follows: Figure 2 As shown, it adopts a bidirectional DC / DC structure, including converter 1, converter 2, converter 3, and an intermediate multi-winding transformer. The positive input terminal of converter 1 is connected to the positive terminal of the traction network, and the negative input terminal is connected to the negative terminal of the traction network. Its output terminal is connected to the high-voltage side port of the multi-winding transformer. The high-voltage side of the multi-winding transformer is connected to the output side of the high-voltage side converter. The low-voltage side of the multi-winding transformer is connected to the input sides of converter 1, converter 2, and converter 3 respectively. The input side of the low-voltage side converter is connected to one low-voltage side port of the multi-winding transformer, and its output side is connected to the energy storage medium.

[0032] The converter m (m=1,2,3) consists of a power inductor L m Capacitor C m Switch S m1 Switch S m2 Switch S m3 and switching transistor S m4 Composition, power inductor L m One end is connected to one end of the high-voltage side of the multi-winding transformer, and the power inductor L m The other end is connected to the switching transistor S m1 The source terminal of the multi-winding transformer is connected to the other end of the high-voltage side of the switching transistor S. m2 and switching transistor S m4 The source of the switch S m1 The source is connected to the switch S. m2 The drain of the switching transistor S m4 The drain is connected to the output inductor L m One end, the switching transistor S m1 and switching transistor S m3 The drain is connected to capacitor C m One end, the switching transistor S m2 and switching transistor S m4 The source of the transistor is connected to the negative terminal of the output side of port m, and the switching transistor S... m1 and switching transistor S m3 The drain of the device is connected to the positive terminal of the output side of port m.

[0033] In this embodiment, the switching transistors of converter 1, converter 2 and converter 3 are all fully controllable semiconductor devices.

[0034] S200 of this embodiment of the invention includes the following sub-steps: S201. Perform transient DC bias calculation on the output shift before and after the operating condition change to determine the initial value of the inductor current before and after the operating condition change. S202. Based on the initial values ​​of the inductor current before and after the operating condition change, calculate the transient DC bias of the inductor current at the corresponding port caused by the phase shift. S203. Replace the transient DC bias of the inductor current with the volt-second value to obtain the corresponding first volt-second difference value.

[0035] In the above process, taking the equivalent circuit between arbitrary ports A and B as the research object (A=1, 2, 3, B=1, 2, 3; A≠B), let its square wave voltages be u. A and u B The voltage amplitudes after conversion to port 1 are U A and U B The shift ratios of the two relative to the square wave voltage u1 at port 1 are D and D, respectively. A and D B The operating condition jump was shifted afterward, respectively. and The equivalent inductance is L AB By observing different combinations of shift ratio changes, the initial value of the inductor current i before the operating condition jump in the equivalent circuit can be obtained. LAB (t0) is shown in Table 1. The transient DC bias is calculated based on the shift ratio, and the initial inductor current i corresponding to the shift ratio is calculated using the pre-derived table of initial inductor current values. L12 (t0) The calculation method for the initial value of the inductor current is the same before and after the operating condition change.

[0036] Table 1: Initial values ​​of inductor current in equivalent circuits under various shift ratio combinations

[0037] Among them, D A and D B Compared to the shifts of the second and third ports before the operating condition change, L AB For equivalent inductance, U is half of the switching cycle. A U is the port voltage of the second port before the operating condition transition. B This is the port voltage of the third port before the operating condition change.

[0038] In a specific embodiment, taking transition type 1 as an example, when the operating condition changes abruptly, the transient DC bias I of the inductor current caused by the phase shift at port 2 is calculated based on the initial value of the inductor current. BiasL12 :

[0039] In the formula, I is the port voltage at port 2 after the operating condition change, referred back to port 1, and k2 is the equivalent power inductance coefficient corresponding to port 2. BiasL12 This indicates the inductor current bias between ports 1 and 2. Since the shift ratio of port 1 relative to itself is 0, the above I can be derived. BiasL12 The expression.

[0040] Furthermore, the transient DC bias of the inductor current is replaced by a volt-second value to obtain the corresponding first volt-second difference value Δf. BiasL12 :

[0041] In one specific embodiment, due to the excessive number of shifts compared to the combination, D A >D B The condition >0 is taken as the operating state before the abrupt change in phase shift. By analyzing the initial value of the equivalent circuit inductor current under different combinations of phase shift changes, the magnitude of the first volt-second product of the transient DC bias caused by phase shift under all abrupt changes in operating conditions can be obtained, as shown in Table 2.

[0042] Table 2: First volt-second difference under various shift ratio combinations

[0043] Embodiment S300 of the present invention includes the following steps: S301, Sample and obtain the operating condition transition time of the second / third port; S302. Based on the time of the operating condition jump, determine the shift ratio and its sign before and after the operating condition jump; S303. Based on the shift ratio and its sign before and after the operating condition change, calculate the volt-second product value of each port under the corresponding shift ratio. S304. Subtract the volt-second product value after the operating condition change from the value before the operating condition change to obtain the corresponding second volt-second difference value.

[0044] In one specific embodiment, let the port 2 shift ratio be D. 12 Greater than 0; Port 3 shift ratio is D 13 The product of the voltages at each port and the power inductor is less than 0; the volt-second products generated by each port voltage on the power inductor are f 11 (t), f 12 (t), f 13(t). Since port 1 does not shift phase, we take the value of the volt-second product at port 1 as t0 when it is 0 and the value of the volt-second product at port 1 as t3 when it is at its maximum. Based on the phase shift ratios corresponding to ports 2 and 3, we set t2 and t5, and then we can derive the expressions for each volt-second product value: Before the operating condition change, when the shift ratio is 0, the volt-second product is:

[0045] Before the operating condition change, when the shift ratio is greater than 0, the volt-second product is:

[0046] Before the operating condition change, when the shift ratio is less than 0, the volt-second product is:

[0047] In the formula, Let be the port voltage of port i after the operating condition change. Compared to the shift of port i before the operating condition change, It is half of the switching cycle. For the current moment, , , , , , , The subscripts i=2,3 correspond to the second and third ports.

[0048] Therefore, the second volt-second difference caused by the switching time at the second / third port is:

[0049]

[0050]

[0051]

[0052] In the formula, ∆F 1i-11 (t) represents the second volt-second difference when port i abruptly changes from the positive shift ratio to the positive shift ratio, ∆F. 1i -00 (t) represents the second volt-second difference when port i abruptly changes from the negative shift ratio to the negative shift ratio, ∆F. 1i -10 (t) represents the second volt-second difference when port i abruptly changes from a positive shift ratio to a negative shift ratio, ∆F. 1i -01 (t) represents the second volt-second difference when port i abruptly changes from a negative shift ratio to a positive shift ratio. Let be the port voltage of port i after the operating condition change. Compared to the shift of port i before the operating condition change, It is half of the switching cycle.

[0053] In the formula for calculating the second volt-second difference, the 0 and 1 in the latter part represent the positive and negative values ​​of the shift ratio, and the order represents before and after the mutation.

[0054] S400 of this embodiment of the invention includes the following sub-steps: S401. Construct a working condition mode classification table to represent the correspondence between different working modes and working states when the working condition changes; wherein, the working modes are divided according to the sign combination and magnitude relationship of the shift before and after the working condition change, and the working states are divided according to the interval of the volt-second product waveform in which the working condition change time is located. S402. Based on the combination of the current working condition transition before and after shift and the interval in the volt-second product waveform at the time of the working condition transition, look up the table in the working condition mode classification table to determine the current working state. S403. Determine the bias suppression strategy based on the current working status; S404. Determine the bias suppression time under the current suppression strategy based on the total volt-second difference value determined by the first volt-second difference value and the second volt-second difference value. The bias suppression time includes a first suppression time and a second suppression time. The first suppression time is the time for executing the bias suppression strategy on the port where the operating condition change occurs, and the second suppression time is the time for executing the bias suppression strategy on another port affected by the operating condition change.

[0055] In one specific embodiment, transient DC bias essentially occurs because the duration of the port voltage's effect on the power inductor changes when the phase shift changes, disrupting the volt-second balance. The volt-second value can be artificially controlled by inverting the positive and negative phases of the square wave voltage for a short period. Inverting the voltage when port 1 is positive decreases the volt-second value; inverting it when port 1 is negative increases the volt-second value. For ports 2 and 3, the voltage effect is the opposite of port 1; inverting the voltage when they are positive increases the volt-second value, and inverting it when they are negative decreases the volt-second value. Furthermore, the rate of increase or decrease of the volt-second value after voltage adjustment at each port is twice that of the corresponding port voltage. During the time interval between different phase shift time products before and after a change in the operating condition of the same port (hereinafter referred to as the volt-second value natural change state), the volt-second value of that port changes naturally. If the phase shift jump occurs within this time interval, the total volt-second value ∆F... all It will change in the opposite direction to its own polarity (i.e., if ∆F at this time) all If it's positive, it will change to negative. This time period is often small, and when the shift occurs within this period, special handling is required. Furthermore, because the shift time t... xSince it cannot be suppressed during specific time periods, this type of state, along with some naturally changing volt-second values, is categorized as a maintenance state.

[0056] Based on this, the working condition classification table is shown in Table 3. According to different working states, different processing methods are selected under different conditions to obtain the bias suppression strategy and bias suppression time Δt1 and Δt2 under the corresponding working conditions.

[0057] Table 3: Operating Mode Classification Table

[0058] in, Compared to the shift of port i before the operating condition change, Compared to the shift of port i after the change in operating conditions, It is half of the switching cycle. The time of the change in operating condition is i=2,3, which correspond to the second port and the third port.

[0059] In S403 of this embodiment, determining the bias suppression strategy includes: When the operating state is operating state 1 / 2, the port voltage of the second / third port where the operating condition change occurs is inverted within the bias suppression time; the bias suppression time is calculated by dividing the total volt-second difference by the volt-second change rate generated by the port voltage inversion. When the operating state is in the maintenance state, the volt-second product of the second / third port waiting for the operating condition to change will naturally cross zero.

[0060] Specifically, when determining the bias suppression strategy, a suppression trigger time threshold is introduced. When the sum of the first volt-second difference and the second volt-second difference is less than the suppression trigger time threshold, transient DC bias suppression is not performed.

[0061] In S500 of this embodiment of the invention, the signals input to the single-phase-shift modulation module are controlled according to the bias suppression times Δt1 and Δt2, so that the switching signals of the switching transistor are adjusted accordingly, and the polarity of the output voltage meets the suppression time requirements of the switching signal.

[0062] In one embodiment of the present invention, such as Figure 3 The diagram shows the operating waveforms of an isolated three-port converter. The switching transistor S of converter 1... 11 and S 14 With the same switching unit drive signal, the switching transistor S 12 and S 23 With the same switching unit drive signal, the switching transistor S 11 and S 12 The drive signals of the switching units are complementary. The switching transistor S of converter 2... 21 and S 24With the same switching unit drive signal, the switching transistor S 22 and S 23 With the same switching unit drive signal, the switching transistor S 21 and S 22 The drive signals of the switching units are complementary. The switching transistor S of converter 3... 31 and S 34 With the same switching unit drive signal, the switching transistor S 32 and S 33 With the same switching unit drive signal, the switching transistor S 31 and S 32 The drive signals of the switching units are complementary.

[0063] The phase shift angles between the drive signals of the switching units at ports 1, 2, and 3 are respectively D 12 D 13 D 23 By controlling the shift compared to D 12 D 13 This allows control over the magnitude and direction of power transmission between each port. When D... ab When D is greater than 0, power is transferred from side a to side b; when D... ab When the value is less than 0, power is transferred from side b to side a. (Where a and b are any two distinct numbers from 1, 2, and 3.) Taking the primary inductor as an example, its inductor current value can be derived as follows:

[0064]

[0065]

[0066] When operating stably, the volt-second balance condition is met, and the inductor current waveform exhibits symmetry in both positive and negative half-cycles. L1 satisfy:

[0067] Combining the above formulas, we can derive Figure 3 The numerical expressions for the inductor current at various times are as follows:

[0068] in:

[0069]

[0070]

[0071] Figure 4This is a schematic waveform of the transient DC bias generated during a change in operating conditions. Figure 5 To correspond to the equivalent volt-second product waveform, the formula for the real-time volt-second product at different ports under different shift ratios can be derived, thus obtaining the volt-second difference ∆F caused by the switching time. 12 .

[0072]

[0073]

[0074]

[0075] Transient DC bias essentially occurs because a change in the phase shift alters the duration of the port voltage's effect on the power inductor, disrupting the volt-second balance. The volt-second value can be artificially controlled by inverting the positive and negative phases of the square wave voltage for a short period. For example... Figure 6 The diagram shown illustrates the basic principle of transient DC suppression. Taking port 1 as an example, it can be seen that the difference in volt-second values ​​during the bias suppression time intervals ∆t1 and ∆t2 is:

[0076] Applying a reverse voltage when the voltage at port 1 is positive will decrease the volt-second value; applying a reverse voltage when the voltage at port 1 is negative will increase the volt-second value. For ports 2 and 3, the effect is the opposite of port 1: applying a reverse voltage when the voltage at port 2 is positive will increase the volt-second value; applying a reverse voltage when the voltage at port 3 is negative will decrease the volt-second value. Furthermore, the rate of increase or decrease in the volt-second value after voltage adjustment at each port is twice the rate of increase of the corresponding port voltage.

[0077] Figure 7 This is the suppression principle diagram for mode ①, operating state 1, with a total volt-second value ∆F. all for:

[0078] ∆f BiasL12 If positive, the current shift is compared to D. 12 The volt-second value in the state is greater than the shift after the jump. The current volt-second value needs to be reduced.

[0079] At this time, the voltage at port 1 is positive, and the volt-second value generated by port 1 is in an upward trend. Adjusting the voltage at port 1 to be negative will reduce the volt-second value it generates. Adjusting the voltage at port 2 to be positive will reduce the volt-second value generated by port 2, since the voltage at port 2 was negative before and after the transition.

[0080] Since the voltage effect at port 1 synchronously affects port 3, the voltage at port 3 needs to be adjusted to be negative to offset the decrease in volt-second value caused by the voltage effect at port 1. Therefore, the required action time ∆t1 for port 1 and port 2, and the required action time ∆t2 for port 3, are respectively:

[0081]

[0082] Figure 8 This is the schematic diagram of the suppression principle for maintaining the state in mode ①. The zero-crossing point of the volt-second value is derived as follows: The transition time t at this point x It is in a state of natural volt-second change and is located at the zero-crossing point of the volt-second value. Previously, suppression could be achieved simply by maintaining the shift ratio until it crossed zero and then releasing it. The corresponding compensation time ∆t1 was:

[0083] The compensation time ∆t1 in this state varies with the jump time t x The value decreases as it approaches zero.

[0084] Figure 9 This is the suppression principle diagram for operating state 2 of mode ①. At this time, the volt-second difference value generated by the phase shift is the same as that in operating state 1 of mode ①, and the volt-second value ∆F generated by the switching time is... 12 for:

[0085] The total volt-second value ∆F at this time all Negative:

[0086] This indicates that the voltages at each port need to be adjusted to increase the current volt-second value, and bias suppression can only be achieved through port 2. Since the voltage at port 2 does not affect port 3, no operation is required at port 3. The corresponding compensation time ∆t1 is:

[0087] Figure 10 This is the schematic diagram for mode ② suppression. During the natural transition of the non-volt-second value in the maintenance state, both the current voltage at port 2 and the voltage at port 2 after the transition are negative. The volt-second value generated by the port 2 voltage is in an upward state. The volt-second value ∆F generated by the switching time... 12 The value is 0, and the total volt-second value ∆F at this time is 0. all for:

[0088] At this time ∆f BiasL12If the value is negative, the current volt-second value needs to be increased to compensate the system.

[0089] Currently, the voltage at port 1 is positive, and the volt-second value generated by port 1 is increasing. Adjusting the voltage at port 1 to be negative will only reduce the generated volt-second value, further increasing the magnitude of the negative volt-second value. Therefore, port 1 cannot be used for compensation at this time. As for port 2, since the voltage at port 2 is negative before and after the transition, inverting the current voltage at port 2 will also cause the volt-second value to increase further in the negative direction. Therefore, compensation cannot be performed at this time. The current output shift ratio should be maintained until the volt-second value crosses zero.

[0090] When the volt-second value in the maintenance state changes state naturally, the shift ratio should also be maintained and the current shift ratio should be output until the volt-second value crosses zero.

[0091] After the natural change of the volt-second value, the jump time t x Upon reaching operating state 1, the volt-second value ∆F generated by the switching time is... 12 for:

[0092] Total volt-second value ∆F all If the value is positive, the voltage at each port needs to be adjusted to reduce the current volt-second value.

[0093] For port 2, the voltage at port 2 is positive before and after the transition, and the volt-second value is decreasing. If the current voltage of port 2 is reversed, it will only increase the current volt-second value, and the volt-second value cannot be compensated by adjusting the voltage of port 2. The voltage of port 1 is positive in operating state 1. Adjusting the voltage of port 1 to be negative will decrease the current volt-second value. The voltage of port 3 is adjusted synchronously to compensate for the effect caused by port 1.

[0094] Then the duration of port 1, ∆t1, and the compensation time of port 3, ∆t2, are respectively:

[0095]

[0096] Figure 11 This is a schematic diagram illustrating the suppression principle of mode ③ of the present invention. The volt-second value ∆f generated by the phase shift is... BiasL12 for:

[0097] When in operating state 1, the total volt-second value ∆F all Equal to the volt-second value ∆f generated by the phase shift BiasL12 If the value is positive, the voltage at each port needs to be adjusted to reduce the current volt-second value.

[0098] For port 2, the voltage at port 2 is positive both before and after the transition, and the volt-second value is decreasing. If the current voltage at port 2 is reversed, it will only increase the current volt-second value, and the volt-second value cannot be compensated by adjusting the voltage at port 2. The voltage at port 1 is positive during the current period and can be adjusted to be negative to decrease the current volt-second value. At the same time, the voltage at port 3 can be adjusted to compensate for the effect caused by port 1.

[0099] Then the duration of port 1, ∆t1, and the compensation time for port 3 are respectively:

[0100]

[0101] Mode ③, the maintenance state, can be divided into two parts. (1) In the maintenance state, before the volt-second value crosses zero, the total volt-second value ∆F all From positive to negative, the shift ratio is maintained until it crosses zero (i.e., Figure 10 (1) Release at the yellow line in the middle to complete the suppression work. (2) In the maintenance state, after the volt-second value crosses zero, the total volt-second value ∆F is released. all If the voltage is negative, the volt-second value needs to be increased, but since the voltage at port 1 is positive, it can only be decreased. The voltage state at port 2 can at most maintain the current volt-second value, but cannot completely suppress the voltage. This would result in the volt-second value being too small when suppression is performed in the next state, causing the switching device's on-time to be less than the minimum on-time limit. Therefore, the shift ratio is maintained until the second half of the cycle, operating state 1, before further processing is performed.

[0102] Figure 12 This is a schematic diagram illustrating the working state 1 and the suppression principle of the maintenance state in mode ④ of the present invention. The volt-second value ∆f generated by the phase shift is... BiasL12 for:

[0103] When in working state 1, the volt-second value ∆F generated by the switching time. 12 If it is 0, then the total volt-second value ∆F all Equal to the volt-second value ∆f generated by the phase shift BiasL12 , is negative.

[0104] At this time, the voltage at port 1 is positive. If it is adjusted to negative, it can only reduce the current volt-second value. Therefore, port 1 cannot be used to compensate for the volt-second gap at port 2. Both the current voltage at port 2 and the voltage at port 2 after the transition are positive, and the resulting volt-second values ​​are decreasing. The current voltage at port 2 can be adjusted to negative to compensate for the volt-second gap at port 2. Port 3 does not require operation. The corresponding compensation time ∆t1 is:

[0105] During the maintenance phase, before the volt-second value crosses zero, the total volt-second value ∆F all The phase shifts from negative to positive, maintaining the phase shift until it reaches the zero point of the volt-second value, at which point the phase shift is released, completing the suppression process.

[0106] During the maintenance phase, after the volt-second value crosses zero, the shift ratio is maintained until working state 2, at which point the suppression operation is performed.

[0107] Figure 13 This is the principle diagram for suppression in mode ④, operating state 2. Adjusting the voltage at port 1 to negative reduces its generated volt-second value. Adjusting the current voltage at port 2 to positive, since the voltage at port 2 is negative before and after the transition, also reduces the generated volt-second value at port 2. The time ∆t1 during which ports 1 and 2 act simultaneously, and the time ∆t2 during which port 3 is adjusted, are respectively:

[0108]

[0109] Figure 14 This is a schematic diagram illustrating the suppression principle of mode ⑤ of the present invention. The volt-second value ∆f generated by the phase shift is... BiasL12 for:

[0110] When in the maintenance state, the shift ratio is maintained until the volt-second value crosses zero, at which point the shift ratio is released, thus completing the suppression operation.

[0111] When entering working state 1, the volt-second value ∆F caused by the switching time is obtained. 12 Total volt-second value ∆F all They are respectively:

[0112]

[0113] ∆F all If the current value is positive, the voltages at each port need to be adjusted to decrease the current volt-second value. At this time, it is impossible to compensate for the volt-second value by adjusting the voltage at port 2. During this period, the voltage at port 1 can be adjusted to be negative, reducing the current volt-second value, and the voltage at port 3 can be adjusted simultaneously to compensate for the effect caused by port 1. Therefore, the effective time ∆t1 of port 1 and the compensation time of port 3 are respectively:

[0114]

[0115] After working state 1 ends, it will enter the volt-second value natural change state again, and will also return to the maintenance state, maintaining the shift ratio until working state 1 in the second half of the cycle is processed again.

[0116] Figure 15 This is a schematic diagram illustrating the suppression principle of mode ⑥ of the present invention. The volt-second value ∆f generated by the phase shift... BiasL12 for:

[0117] Similar to mode ⑤, mode ⑥ also directly enters the natural volt-second value transition state at the beginning of the cycle. At this time, the volt-second value gradually decreases, maintaining the shift ratio until it is released when the volt-second value crosses zero, thus completing the suppression work.

[0118] Under operating state 1, the volt-second value ∆F caused by the switching time is obtained. 12 Total volt-second value ∆F all They are respectively:

[0119]

[0120] ∆F all If the voltage is negative, the voltages at each port need to be adjusted to increase the current volt-second value. At this time, the voltage at port 1 is positive, so it can only decrease the current volt-second value, and therefore cannot be used to compensate for the volt-second gap. Both the current voltage at port 2 and the voltage at port 2 after the transition are positive, and their resulting volt-second values ​​are decreasing. Adjusting the current voltage at port 2 to negative will compensate for the volt-second gap at port 2; port 3 requires no operation. The corresponding compensation time ∆t1 is:

[0121] After working state 1 ends, it will enter the volt-second value natural change state again, which is also a maintenance state. The shift ratio is maintained until the volt-second value of the second half of the cycle crosses zero, at which point the shift ratio is released, thus completing the suppression work.

[0122] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0123] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A new energy access-type TAB DC bias suppression method based on operating condition mode classification, characterized in that, To suppress transient DC bias generated when a single-port switching occurs in an isolated three-port converter, the following steps are included: S100. Obtain the port voltage of the second / third port in the isolated three-port converter, compare it with the corresponding reference voltage to obtain the voltage error signal, and then determine the shift between the switching transistor drive signals of the first port and the second / third port before and after the operating condition change. S200. Perform transient DC calculations on the phase shift ratio before and after the operating condition jump to obtain the first volt-second difference value caused by the phase shift at the second / third port. S300: Sample and obtain the operating condition switching time of the second / third port, and perform offset calculation by combining the shift ratio before and after the operating condition switching to obtain the second volt-second difference value of the second / third port caused by the switching time; S400. Based on the first volt-second difference value and the second volt-second difference value, combined with the working mode and working status when the current working condition changes, determine the bias suppression strategy and bias suppression time of the second / third port under the corresponding working condition. S500: Based on the bias suppression strategy and bias suppression time, determine the actual output phase shift angle between the drive signals of the first port and the second / third port switching transistors, and generate the corresponding switching signal after single-phase-shift PWM modulation, thereby realizing the transient DC bias suppression of the isolated three-port converter TAB.

2. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 1, characterized in that, S200 includes the following steps: S201. Perform transient DC bias calculation on the output shift before and after the operating condition change to determine the initial value of the inductor current before and after the operating condition change. S202. Based on the initial values ​​of the inductor current before and after the operating condition change, calculate the transient DC bias of the inductor current at the corresponding port caused by the phase shift. S203. Replace the transient DC bias of the inductor current with the volt-second value to obtain the corresponding first volt-second difference value.

3. The renewable energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 2, characterized in that, In S201, the calculation method for the initial value of the inductor current is the same before and after the operating condition change. Before the operating condition change, the initial value of the inductor current is calculated based on the combination of the shift ratios, including: Type 1: When , , At that time, the initial value of the inductor current i LAB (t0) is: Type 2: When , , At that time, the initial value of the inductor current i LAB (t0) is: Type 3: When At that time, the initial value of the inductor current i LAB (t0) is: Type 4: When At that time, the initial value of the inductor current i LAB (t0) is: Type 5: When At that time, the initial value of the inductor current i LAB (t0) is: Type 6: When At that time, the initial value of the inductor current i LAB (t0) is: Type 7: When At that time, the initial value of the inductor current i LAB (t0) is: Type 8: When At that time, the initial value of the inductor current i LAB (t0) is: Type 9: When At that time, the initial value of the inductor current i LAB (t0) is: In the formula, D A and D B Compared to the shifts of the second and third ports before the operating condition change, L AB For equivalent inductance, U is half of the switching cycle. A U is the port voltage of the second port before the operating condition transition. B This is the port voltage of the third port before the operating condition change.

4. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 1, characterized in that, S300 includes the following steps: S301, Sample and obtain the operating condition transition time of the second / third port; S302. Based on the time of the operating condition jump, determine the shift ratio and its sign before and after the operating condition jump; S303. Based on the shift ratio and its sign before and after the operating condition change, calculate the volt-second product value of each port under the corresponding shift ratio. S304. Subtract the volt-second product value after the operating condition change from the value before the operating condition change to obtain the corresponding second volt-second difference value.

5. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 4, characterized in that, In S303, the calculation method for the volt-second product value before and after the operating condition change is the same. Before the operating condition change, when the shift ratio is 0, the volt-second product is: Before the operating condition change, when the shift ratio is greater than 0, the volt-second product is: Before the operating condition change, when the shift ratio is less than 0, the volt-second product is: In the formula, Let be the port voltage of port i after the operating condition change. Compared to the shift of port i before the operating condition change, It is half of the switching cycle. For the current moment, , , , , , , The subscripts i=2,3 correspond to the second and third ports.

6. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 5, characterized in that, In S304, the second volt-second difference value caused by the switching time for the second / third port is: In the formula, ∆F 1i-11 (t) represents the second volt-second difference when port i abruptly changes from the positive shift ratio to the positive shift ratio, ∆F. 1i -00 (t) represents the second volt-second difference when port i abruptly changes from the negative shift ratio to the negative shift ratio, ∆F. 1i -10 (t) represents the second volt-second difference when port i abruptly changes from a positive shift ratio to a negative shift ratio, ∆F. 1i -01 (t) represents the second volt-second difference when port i abruptly changes from a negative shift ratio to a positive shift ratio. Let be the port voltage of port i after the operating condition change. Compared to the shift of port i before the operating condition change, It is half of the switching cycle.

7. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 1, characterized in that, S400 includes the following steps: S401. Construct a working condition mode classification table to represent the correspondence between different working modes and working states when the working condition changes; wherein, the working modes are divided according to the sign combination and magnitude relationship of the shift before and after the working condition change, and the working states are divided according to the interval of the volt-second product waveform in which the working condition change time is located. S402. Based on the combination of the current working condition transition before and after shift and the interval in the volt-second product waveform at the time of the working condition transition, look up the table in the working condition mode classification table to determine the current working state. S403. Determine the bias suppression strategy based on the current working status; S404. Determine the bias suppression time under the current suppression strategy based on the total volt-second difference value determined by the first volt-second difference value and the second volt-second difference value. The bias suppression time includes a first suppression time and a second suppression time. The first suppression time is the time for executing the bias suppression strategy on the port where the operating condition change occurs, and the second suppression time is the time for executing the bias suppression strategy on another port affected by the operating condition change.

8. The method for suppressing DC bias in new energy access-type TAB based on operating condition mode components according to claim 8, characterized in that, In step S401, the correspondence between working modes and working states in the working condition mode classification table includes: Working Mode 1: The corresponding working states include: Working status 1: Maintaining status: Working Status 2: Working Mode 2: The corresponding working states include: Maintaining status: Working status 1: Working Mode 3: The corresponding working states include: Working status 1: Maintaining status: Working Mode 4: The corresponding working states include: Working status 1: Maintaining status: Working Status 2: Working Mode 5: The corresponding working states include: Maintaining status: Working status 1: Maintaining status: Working Mode 6: The corresponding working states include: Maintaining status: Working status 1: Maintaining status: In the formula, Compared to the shift of port i before the operating condition change, Compared to the shift of port i after the change in operating conditions, It is half of the switching cycle. The time of the change in operating condition is i=2,3, which correspond to the second port and the third port.

9. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 8, characterized in that, In step S403, determining the bias suppression strategy includes: When the operating state is operating state 1 / 2, the port voltage of the second / third port where the operating condition change occurs is inverted within the bias suppression time; the bias suppression time is calculated by dividing the total volt-second difference by the volt-second change rate generated by the port voltage inversion. When the operating state is in the maintenance state, the volt-second product of the second / third port waiting for the operating condition to change will naturally cross zero.

10. The new energy access-type TAB DC bias suppression method based on operating condition mode classification according to claim 1, characterized in that, In S400, when determining the bias suppression strategy, a suppression trigger time threshold is introduced. When the sum of the first volt-second difference and the second volt-second difference is less than the suppression trigger time threshold, transient DC bias suppression is not performed.

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