A bidirectional DCDC circuit uninterrupted control method

Abstract

The application relates to a bidirectional DCDC circuit uninterrupted control method. The bidirectional DCDC circuit adopts a novel and unique topological structure formed by conventional switching devices, cooperates with an uninterrupted control method, and a charging (discharging) PID, so that continuous charging and discharging of a wider voltage are realized, and the control is simple and the reliability is high.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power electronic devices, and particularly relates to an uninterrupted control method for a bidirectional DC / DC circuit. BACKGROUND

[0002] In recent years, the battery energy storage industry has developed rapidly. In order to pursue higher energy density and reduce system cost, the voltage level of the battery compartment is getting higher and higher. A few years ago, the voltage range of the battery compartment was generally 200V-650V. In recent years, the voltage has risen to 1000V or even higher. The battery compartment charging and discharging equipment matched with it is generally composed of a power storage converter (PCS) + bidirectional DC / DC circuit. The power storage converter (PCS) can convert the three-phase AC 380V of the power grid into a stable DC terminal voltage DC 650V, and can also convert the energy of the DC terminal DC 650V to the three-phase power grid. In order to stabilize the DC terminal voltage, the energy flows automatically in both directions, which is the main function of the PCS. The bidirectional DC / DC circuit is a DC-to-DC converter. When charging the battery, the DC / DC power supply converts the DC 650V voltage output by the PCS into a DC 200V-DC 1500V adjustable voltage to charge the battery. When discharging, the DC / DC power supply converts the battery terminal voltage to 650V to discharge the DC terminal. When the DC terminal voltage is greater than 650V, the PCS automatically converts the DC terminal energy to the three-phase power grid.

[0003] The commonly used bidirectional DC / DC electrical topology structure is shown in Figure 1 The DC terminal (left end) is connected to the PCS DC terminal, and the voltage is DC 650V. The battery terminal of the bidirectional DC / DC is set to a range of DC 200V-DC 1500V. Energy can flow from the DC terminal to the battery terminal, and also from the battery terminal to the DC terminal.

[0004] The inductance L1 current flows from left to right as the positive direction (charging direction), and from right to left as the reverse direction (discharging direction). When working in the positive direction, the right end of the bidirectional DC / DC unit can output a high or low DC voltage: Q21 is always on, Q1 is adjusted, and Q2 is freewheeling, which can realize step-down output; Q1 is always on, Q22 is adjusted, and Q21 is freewheeling, which can realize step-up output. When working in the reverse direction, the left end of the bidirectional DC / DC unit can output a high or low DC voltage: Q1 is always on, Q21 is adjusted, and Q22 is freewheeling, which can realize step-down output; Q21 is always on, Q2 is adjusted, and Q1 is freewheeling, which can realize step-up output.

[0005] The disadvantages of the existing bidirectional DC / DC circuit are:

[0006] 1. High cost:

[0007] FromFigure 1 It can be seen that, whether in the positive direction step-down output or in the reverse direction step-up to the DC end DC650V, the highest voltage borne by the two ends of Q1 and Q2 switch tubes is 650V, and according to the principle of selecting a tube with about 2 times the working voltage, Q1 and Q2 switch tubes can be selected as IGBT with a rated voltage of DC1200V. The battery end bridge arm is different, whether in the positive direction step-up charging or in the reverse direction step-down discharging, the two ends of Q21 and Q22 switch tubes will bear a voltage of DC1500V, and according to the principle of selecting a tube with 2 times the working voltage, Q21 and Q22 switch tubes need to use IGBT with a voltage grade of DC3000V. The IGBT with DC3000V belongs to an unconventional product, and according to the principle of selecting a tube nearby, IGBT with DC3300V needs to be selected, which is very expensive, and the price of one such IGBT is about 10 times that of IGBT with a rated voltage of DC1700V or DC1200V.

[0008] 2. Large switching stress of switch tube, easy to damage:

[0009] The voltage at the two ends of Q21 and Q22 tubes is DC1500V, and when turned on and off, the voltage at the two ends of the tube changes from 0V to 1500V when turned off, and changes from DC1500V to 0V when turned on. If the turn-on and turn-off time is calculated as 2us, Such high dv / dt can easily damage the IGBT.

[0010] 3. There is a repeated switching phenomenon when step-up and step-down switching, resulting in repeated fluctuations of charging and discharging current:

[0011] If the battery needs to be charged from 400V to 800V, the power supply first charges the battery in the positive direction, Q21 is always on, Q1 is adjusted, and Q2 is freewheeling, which can realize charging below DC650V. As the charging proceeds, the battery voltage becomes higher, and when the battery voltage rises to DC650V, Q21 is always on, Q1 is adjusted, and Q2 is freewheeling, which cannot charge, and Q1 is always on, Q22 is adjusted, and Q21 is freewheeling, which can realize step-up charging. After switching to step-up charging, due to the instantaneous interruption of energy, the output voltage will be less than DC650V again, and the system will switch to step-down charging again, and when charged to DC650V again, it will switch to step-up mode. Such repeated switching results in a sharp fluctuation of current when charging near DC650V. SUMMARY

[0012] To avoid the shortcomings of traditional bidirectional DCDC, realize wider voltage charging and discharging requirements, and reduce costs and improve the reliability of the power supply.

[0013] A new type of bidirectional DCDC circuit main electrical topology is proposed, which left end (DC end) is two-level bridge arm, right end (battery end) is three-level bridge arm. The DC end adopts two-level mode, which is composed of the E pole of switch tube Q1 and the C pole of switch tube Q2, and the capacitor C1 is connected across the first bridge arm. The battery end adopts three-level mode, which is composed of the C pole and E pole of switch tubes Q21, Q22, Q23 and Q24, and the capacitors C2 and C3, and the midpoint of the capacitor series is connected between the E pole of Q22 and the C pole of Q23 through a wire. One end of the inductor L1 is connected between the E pole of Q1 and the C pole of Q2, and the other end is directly connected between the E pole of Q21 and the C pole of Q22 through the current sensor Am1, and the ground (DC-) of the DC end is connected between the E pole of Q23 and the C pole of Q24. As shown in Figure 2 .

[0014] In the new type of bidirectional DCDC circuit, the left end voltage is constant 650V, which is connected to the DC bus end of PCS; the right end voltage is 200V-1500V, which is connected to the battery end. The bidirectional DCDC circuit is divided into charging direction and discharging direction according to the energy flow direction. The charging direction is that the energy flows from the left end of the power supply to the right end, and the discharging direction is that the energy flows from the right end to the left end. The principle of the conventional control method of the bidirectional DCDC is as follows.

[0015] I. Control principle in charging direction:

[0016] When working in the charging direction, if the charging current is set to 100A, the charging target voltage is 1000V, and the battery voltage is 500V when the charging starts. For this, Q21 and Q24 need to be always on, Q1 needs to be adjusted, and Q2 needs to be freewheeling to realize the battery charging below the left end voltage 650V. As the battery voltage gradually rises, when the battery voltage rises to 650V, even if Q1 is fully on, the battery cannot be charged. At this time, the boost circuit needs to be started, that is, Q1 is always on, Q22 and Q23 are adjusted, and Q21 and Q24 are freewheeling to realize the boost output.

[0017] From the above control principle can be seen, when the battery voltage is less than 650V, the PID adjusts the duty cycle of Q1, when the battery voltage is equal to the left end voltage of the power supply, because the two end voltage is equal, the current is zero, cannot continue to charge; Greater than 650V, the PID adjusts the duty cycle of Q22 and Q23, which is the boost circuit in the charging direction. Because of this, the conventional control method is to take the left end voltage of the power supply as the dividing line, and design two independent PID control algorithms, one PID forms a closed loop when the battery voltage is less than the left end voltage, and continuously adjusts the duty cycle of Q1 switch tube, the greater the duty cycle, the greater the charging current, until the duty cycle value is equal to the period Period, that is, Q1 is fully on and cannot continue to charge. When it is detected that the battery voltage and the left end voltage are equal or close, the control center closes the first set of PID and starts the second set of PID. The target voltage of the second PID and the control object are different from the first set, the target voltage is the final voltage of the charging, and the control object is the boost switch tube of the right bridge arm, at this time Q1 is fully on, and the duty cycle of Q22 and Q23 is adjusted. The two independent PIDs in the charging direction are shown in Figure 2-1 and Figure 2-2 .

[0018] II. Control principle in discharging direction:

[0019] When working in the discharging direction, if the discharging current is set to 100A, the discharging is stopped when the battery end voltage is 300V, and the battery voltage is 1000V when discharging starts. For this, Q1 needs to be constantly on, Q21 and Q24 need to be adjusted, Q22 and Q23 need to be freewheeling, and the discharge of the battery when the battery end voltage is greater than 650V needs to be realized. As the battery voltage gradually decreases, when it decreases to 650V, even if Q21 and Q24 are fully on, the battery cannot continue to discharge. At this time, the boost circuit needs to be started, that is, Q21 and Q24 are constantly on, Q2 is adjusted, and Q1 is freewheeling, to realize boost output.

[0020] From the above, when the battery voltage is greater than 650V, the PID adjusts the duty cycle of Q21 and Q24, when the battery voltage is equal to the left end voltage of the power supply, the current is zero, and cannot continue to discharge; When less than 650V, the PID adjusts the duty cycle of Q2. Because of this, the conventional control method is to take the left end voltage of the power supply as the dividing line, and design two independent discharge PID control logics, the first set of PID is used when the battery voltage is greater than the left end voltage, and the duty cycle of Q21 and Q24 is adjusted; When it is detected that the battery voltage and the left end voltage of the power supply are equal or close, the first set of PID is closed and the second set of PID is started, and the duty cycle of Q2 is adjusted. The principle is similar to the charging direction, which will not be described in detail here.

[0021] The disadvantages of the bidirectional DCDC circuit using the above control method:

[0022] 1. The method of designing two independent PIDs with the left end voltage of the power supply as the demarcation line has the problem of discontinuity of charging (discharging) current near the demarcation line, which affects the battery or system. For example, when charging, the charging current is 0A when the battery voltage is charged to the left end voltage of the power supply, and after 0A, the second set of PID regulation of the voltage boost is started, and the current slowly rises to the set current value.

[0023] 2. The control is complex, and the demarcation line voltage needs to be detected constantly, two sets of PIDs and two sets of parameters are needed, especially when the target voltage is equal to the voltage at the other end, there is a repeated switching or normal working condition.

[0024] 3. The dynamic response is poor, and when the two sets of PIDs are switched, the two sets of parameters cannot seamlessly connect, and it takes a period of time to enter the steady state after switching to the steady state PID according to the requirements. In the switching process, the system has poor dynamic response.

[0025] 4. There is a repeated switching phenomenon when the voltage boost and voltage drop are switched, which causes the charging and discharging voltage and current to fluctuate near the demarcation line, which causes safety hazards to the power supply itself and the system.

[0026] To solve the above problems, on the basis of the topology of the bidirectional DCDC circuit of the present application, an uninterrupted control method of the bidirectional DCDC circuit is proposed, which includes setting the difference between the given output voltage Uref* of the bidirectional DCDC circuit and the actual output voltage Uout to PI (proportional integral) regulation to output the given output current command Iref*, and then setting the difference between the command Iref* and the actual output current to PI regulation to output the duty cycle output value 0≤DuR<2Period, wherein DuR is the duty cycle output value and Period is the period; when the PID calculates a new value, the control system detects whether DuR is less than 1*Period, if yes, the switch tube Q2 of the first bridge arm is closed, all switch tubes of the second bridge arm are closed, the new duty cycle DuRN=DuR, and then the value of DuRN is updated to the duty cycle register of the switch tube Q1; if not, the switch tube Q1 of the first bridge arm is turned on, the switch tube Q2 is closed, the new duty cycle DuRN=DuR-Period, and then the value of DuRN is updated to the duty cycle register of the switch tube Q22 and the switch tube Q23, and the switch tube Q21 and the switch tube Q24 are closed.

[0027] Advantages of the present application:

[0028] 1. The PID output value is adjusted to twice the range, and then the output value is classified by logical comparison method, which truly realizes a new type of bidirectional DCDC (left two levels, right three levels) uninterrupted boost and buck control, and provides protection for wide voltage power supply.

[0029] 2. The charging (discharging) direction only needs a set of PID to solve, saves the resource of MCU, and improves the system reliability.

[0030] 3. The low voltage end adopts two-level structure, the high voltage end adopts three-level structure, realizes the charging and discharging demand of wider voltage, effectively solves the problem of excessive stress of switch tube, maximally reduces the power cost, and indirectly improves the reliability of the power supply.

[0031] 4. The switching frequency is indirectly improved when charging and boosting and discharging, so that the power system ripple current is reduced.

[0032] In the application, the direct current end voltage of the bidirectional DCDC circuit is less than 800V, and the maximum voltage range of the battery end is greater than 1000V. On this basis, as another improvement scheme, the switch tube is configured as IGBT to achieve reliable switching. Further, the upper limit of the battery end output voltage of the bidirectional DCDC circuit is configured as DC 1500V, and the switch tube of the battery end of the bidirectional DCDC circuit adopts 1700V IGBT. Further, the direct current end of the bidirectional DCDC circuit is configured as DC 650V, and the switch tube of the direct current end of the bidirectional DCDC circuit adopts 1200V IGBT.

[0033] In the application, the uninterrupted control method is configured to associate two sets of independent control objects with a set of PID control algorithms. The PID control algorithm adopts voltage outer loop plus current inner loop, and a logic judgment is set at the PID output end. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A commonly used bidirectional DCDC electrical topology diagram is shown;

[0035] Figure 2 A bidirectional DCDC electrical topology diagram of the application is shown;

[0036] Figure 2-1 The control object and control block diagram below the demarcation line are shown;

[0037] Figure 2-2 The control object and control block diagram above the demarcation line are shown;

[0038] Figure 3 A charging and voltage reduction electrical simulation diagram is shown;

[0039] Figure 4 A charging and voltage reduction output voltage waveform is shown;

[0040] Figure 5 A charging and voltage reduction switch tube upper voltage waveform is shown;

[0041] Figure 6 A charging and voltage reduction electrical simulation diagram is shown;

[0042] Figure 7 The charging boost output voltage waveform is shown;

[0043] Figure 8 The charging boost switch tube upper voltage waveform is shown;

[0044] Figure 9 The charging boost trigger pulse monitoring is shown;

[0045] Figure 10 The waveform diagram of the switching frequency is shown;

[0046] Figure 11 The energy storage charge and discharge power supply block diagram is shown;

[0047] Figure 12 The logic block diagram of uninterrupted control is shown;

[0048] Figure 13 The charging direction electrical simulation model is shown;

[0049] Figure 14 The charging direction (0-1000V) output voltage waveform is shown;

[0050] Figure 15 The charging direction switch tube trigger pulse is shown. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0052] The main electrical topology of the bidirectional DCDC circuit of the present application is shown in Figure 2 The direct current end adopts a two-level mode, and is composed of a first bridge arm formed by the E pole of a switch tube Q1 and the C pole of a switch tube Q2, and a capacitor C1 connected across the first bridge arm. The battery end adopts a three-level mode, and is composed of a second bridge arm formed by the C poles and E poles of switch tubes Q21, Q22, Q23 and Q24 connected in sequence, and capacitors C2 and C3, and the midpoint of the series connection of the capacitors is connected by a wire between the E pole of Q22 and the C pole of Q23. One end of an inductor L1 is connected between the E pole of Q1 and the C pole of Q2, and the other end is directly connected between the E pole of Q21 and the C pole of Q22 after passing through a current sensor Am1. The ground (DC-) of the direct current end is connected between the E pole of Q23 and the C pole of Q24. The current for closed-loop control comes from the folding value of the current sampling at the inductor position between the two bridge arms, and no current sensor needs to be added at the two ends.

[0053] The current of inductor L1 is taken as the positive direction (charging direction) from left to right, and the negative direction (discharging direction) from right to left. When working in the positive direction, the right end of the bidirectional DC / DC unit can output DC voltage which can be high or low: Q21 and Q24 are always on, Q1 is regulated, and Q2 is freewheeling, so that the voltage can be stepped down; Q1 is always on, Q22 and Q23 are regulated, and Q21 and Q24 are freewheeling, so that the voltage can be stepped up. When working in the negative direction, the left end of the bidirectional DC / DC unit can output DC voltage which can be high or low: Q1 is always on, Q21 and Q24 are regulated, and Q22 and Q23 are freewheeling, so that the voltage can be stepped down; Q21 and Q24 are always on, Q2 is regulated, and Q1 is freewheeling, so that the voltage can be stepped up. The following is illustrated by simulation of charging and voltage stepping down and charging and voltage stepping up.

[0054] Figure 3 The electrical simulation of the circuit topology of the application when charging and voltage stepping down (output 500V) is shown, Figure 4 The output voltage waveform of the circuit topology of the application when charging and voltage stepping down is shown, Figure 5 The voltage waveform on the switch tube when charging and voltage stepping down is shown. From Figure Five It can be seen from the output that the CE voltage of all the switch tubes is not high.

[0055] Figure 6 The electrical simulation of the circuit topology of the application when charging and voltage stepping up (output 1500V) is shown, Figure 7 The output voltage waveform of the circuit topology of the application when charging and voltage stepping up is shown, Figure 8 The voltage waveform on the switch tube when charging and voltage stepping up is shown. From Figure 8 It can be seen from the output that the CE voltage of all the switch tubes is not high, and the CE voltage of the switch tube at the battery end is half of the output voltage (DC 1500V), i.e. 750V. It can be seen that after adopting this topology structure, the switching stress of the switch tube is obviously reduced, and the system reliability is improved; after the voltage is reduced, the IGBT of 1200V can be used at the DC end, and the IGBT of 1700V can be used at the battery end, both of which are conventional models, effectively reducing the cost of the power supply.

[0056] For the problem of repeated switching from voltage stepping down to voltage stepping up or from voltage stepping up to voltage stepping down, whether for the positive direction (charging direction) or the negative direction (discharging direction), when working in either of the voltage stepping down mode and the voltage stepping up mode, if the battery end voltage is close to the DC end voltage (e.g. the difference is within a certain range), the application reduces or increases the given voltage of the DC end (the DC end of the PCS) by a certain value, and then switches to the other mode. For example, when charging and voltage stepping down, if the battery voltage rises to be close to DC 650V, the control system reduces the given voltage of the DC end of the PCS, and then switches to the mode of charging and voltage stepping up. In this way, repeated switching is avoided.

[0057] Figure 9An electrical simulation of the charge boost trigger pulse monitoring is shown, Figure 10 A waveform diagram of the switching frequency is shown from Figure 10 It can be seen that the frequency of the three-level bridge arm output end (on the inductor L1) voltage is twice the switching frequency of the switching tube, therefore, by using this topology, the switching frequency is indirectly increased, and the output ripple of the power supply is reduced.

[0058] As Figure 11 The energy storage charging power supply of the application is composed of a PCS energy storage converter and a bidirectional DCDC circuit, the direct current of the PCS energy storage converter is connected with the direct current end of the bidirectional DCDC circuit, which can not only convert the grid energy into direct current to charge the battery, but also can convert the battery energy to the grid, and the energy flows bidirectionally. The bidirectional DCDC circuit has wide voltage output, which can charge and discharge the battery compartment of various voltage grades. The main electrical topology of the energy storage charging power supply has the following advantages:

[0059] 1. The two-level bridge arm is used in cooperation with the three-level bridge arm to realize the charging and discharging demand of a wider voltage, and effectively solve the problem of excessive stress of the switching tube;

[0060] 2. Low cost, all switching devices can use conventional switching devices, effectively reducing the cost;

[0061] 3. Improved reliability, reduced switching stress, and indirectly improved reliability of the power supply;

[0062] 4. Before the boost-buck switching, the given voltage of the PCS is appropriately changed to ensure the repeated false switching of the system.

[0063] 5. During the charging boost and discharging buck, the switching frequency is indirectly increased, and the ripple current of the power supply system is reduced.

[0064] Due to the difference between the given object and the controlled object, the conventional control method is to set two different PIDs in the charging (discharging) direction, and each time to independently constitute a closed loop, causing the boost-buck switching time to be discontinuous, and unable to continuously output, and even fluctuating back and forth at the switching point. To solve this problem, based on the topology structure of the above bidirectional DCDC circuit, the control logic is set as Figure 12 shown, including:

[0065] The difference between the given output voltage Uref* of the bidirectional DCDC circuit and the actual output voltage Uout is PI (proportional integral) adjusted to output the given output current command Iref*, and the difference between the command Iref* and the actual output current is PI adjusted to output the duty cycle output value of 0≤DuR<2Period, wherein DuR is the duty cycle output value, and Period is the period;

[0066] When the PID calculates a new value, the control system detects whether DuR is less than 1*Period, if yes, the control switch tube Q2 of the first bridge arm is closed, all switch tubes of the second bridge arm are closed, the new duty cycle DuRN=DuR, and then the value of DuRN is updated to the duty cycle register of switch tube Q1; if not, the control switch tube Q1 of the first bridge arm is turned on, the switch tube Q2 is closed, the new duty cycle DuRN=DuR-Period, and then the value of DuRN is updated to the duty cycle register of switch tubes Q22 and Q23, and switch tubes Q21 and Q24 are closed.

[0067] Figure 12 In the embodiment, a set of PID is arranged in the whole charging (discharging) direction, and the PID is prepared for continuous and uninterrupted control. At this time, the PID output is not the duty cycle of 0-Period, but is changed to the output value of 0-2*Period. If the value regulated by the PID at this time is 1.5*Period, it indicates that the charging (discharging) direction needs to output the duty cycle of 1.5 times of the period to meet the regulation requirement at this time, but the duty cycle value greater than or equal to the period cannot be expressed in the same control object, so at this time, 1.5 times of the period is divided into 1+0.5 periods, the front 1 indicates that the switch tube Q1 of the charging (discharging) direction is turned on, and the rear 0.5 indicates that the switch tubes Q22 and Q23 of the charging (discharging) direction are regulated by PWM. Therefore, when the PID calculates a new value, the MCU needs to make a size judgment of the output value, and when it is detected that the output value DuR is greater than or equal to the period, it indicates that the regulation of the charging (discharging) has been switched to the right bridge arm. The right bridge arm Q1 is turned on, the Q2 is closed, the new duty cycle DuRN=DuR-Period, then the value of DuRN is updated to the duty cycle register of Q22 and Q23, and Q23 and Q24 are closed.

[0068] The principle of the boost of the charging (discharging) is that the inductor stores energy and then releases the energy, and in this process, the more energy the inductor stores, the more energy it releases. Therefore, in order to obtain higher voltage, the value of DuR regulated by the PID is larger, the time of turning on in the period is longer, the inductor stores more energy, and the released energy is more. Uout is the output voltage, Uin is the input voltage, L is the inductance, and di / dt is the inductance current change. Because the inductor stores energy and releases energy, and the integral is considered, the regulation output value of the PID cannot reach 2*Period, and in the embodiment, at least 0.1*Period is left for releasing energy.

[0069] The electrical simulation model is established by taking the charging direction as an example, the voltage at the left end is DC 650V, the target output voltage at the right end is DC 1000V, the current limiting value is 100A, a 5Ω resistor is arranged, and the frequency is 5kHz. As shown in Figure 13 .

[0070] From the trigger waveform of Q1, Q22, Q23, it can be seen that the switching is crisp and clean, and there is no repeated switching phenomenon, which makes the voltage and current stable output. Figure 13

[0071] The control during discharging is similar to that during charging, and the PID regulation output of 0-2*Period is adopted, and the comparator is automatically switched to the control of the corresponding bridge arm seamlessly. Whether it is step-up or step-down, the same PID parameter is used, and the seamless switching is truly achieved.

[0072] Figure 14 The output voltage waveform in the charging direction (0-1000V) is shown. From the voltage waveform in the charging direction, it can be seen that when the output voltage is equal to the input voltage (650V), it is smooth and there is no any pause.

[0073] Figure 15 The switch tube trigger pulse in the charging direction is shown. From the trigger waveform of Q1, Q22, Q23, it can be seen that the switching is crisp and clean, and there is no repeated switching phenomenon, which makes the voltage and current stable output. Figure 15

[0074] The control during discharging is similar to that during charging, and the PID regulation output of 0-2*Period is adopted, and the comparator is automatically switched to the control of the corresponding bridge arm seamlessly. Whether it is step-up or step-down, the same PID parameter is used, and the seamless switching is truly achieved.

[0075] The advantages of the uninterrupted control method of the bidirectional DCDC circuit of the application are:

[0076] 1. The PID output value is adjusted to twice the range, and the output value is classified by logical comparison method, which truly realizes a new type of bidirectional DCDC (two levels on the left and three levels on the right) uninterrupted step-up and step-down control, and provides guarantee for the non-polar adjustable wide voltage power supply.

[0077] 2. Only one set of PID is needed for charging (discharging) direction, which saves the resources of MCU and improves the system reliability.

[0078] 3. Seamless switching is realized when the battery voltage is equal to the DC terminal voltage, and there is no mutation in the voltage waveform.

[0079] ​​In the present application, the control system adopts DSP28335, and the running frequency is 150MHz; the control system architecture adopts 1*DPS+1*FPGA mode, and the two chips communicate with each other through parallel port, and directly share registers; the PID algorithm is realized in the DSP, the calculated value is sent to the FPGA for judgment and comparison, and then output to the corresponding IO port, and then the IGBT is controlled through the driving circuit, and the switching frequency is 5kHz, or 1.5kHz-6kHz.

[0080] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not a limitation on the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for uninterrupted control of a bidirectional DCDC circuit, characterized in that: the bidirectional DCDC circuit comprises a switch tube Q1, a switch tube Q2, a switch tube Q21, a switch tube Q22, a switch tube Q23, a switch tube Q24, a capacitor C1, a capacitor C2, a capacitor C3 and an inductor L1; the DC end of the bidirectional DCDC circuit adopts a two-level mode, the positive input end of the DC end of the bidirectional DCDC circuit is connected to the C pole of the switch tube Q1, the E pole of the switch tube Q1 and the C pole of the switch tube Q2 are connected, the ground of the DC end of the bidirectional DCDC circuit is connected to the E pole of the switch tube Q2, the switch tube Q1 and the switch tube Q2 form a first bridge arm, and the capacitor C1 is connected across the first bridge arm; the battery end of the bidirectional DCDC circuit adopts a three-level mode, and a second bridge arm is formed by the switch tube Q21, the switch tube Q22, the switch tube Q23, the switch tube Q24, and the capacitors C2 and C3, the C pole and the E pole of the switch tube Q21, the switch tube Q22, the switch tube Q23 and the switch tube Q24 are connected in sequence, the midpoint of the series connection of the capacitors C2 and C3 is connected between the E pole of the switch tube Q22 and the C pole of the switch tube Q23; one end of the inductor L1 is connected between the E pole of the switch tube Q1 and the C pole of the switch tube Q2, and the other end is connected between the E pole of the switch tube Q21 and the C pole of the switch tube Q22, and the ground of the DC end of the bidirectional DCDC circuit is connected between the E pole of the switch tube Q23 and the C pole of the switch tube Q24; the uninterrupted control method comprises setting the difference between the given output voltage Uref* of the bidirectional DCDC circuit and the actual output voltage Uout to perform PI regulation to output a given output current command Iref*, and then setting the difference between the command Iref* and the actual output current to perform PI regulation to output a duty cycle output value of 0≤DuR<2Period, wherein DuR is the duty cycle output value, and Period is the period; when the PID calculates a new value, it is detected whether DuR is less than 1*Period, if yes, the switch tube Q2 of the first bridge arm is controlled to be off, all the switch tubes of the second bridge arm are controlled to be off, a new duty cycle DuRN=DuR, and then the value of DuRN is updated to the duty cycle register of the switch tube Q1; if not, the switch tube Q1 of the first bridge arm is controlled to be on, the switch tube Q2 is controlled to be off, a new duty cycle DuRN=DuR-Period, and then the value of DuRN is updated to the duty cycle registers of the switch tube Q22 and the switch tube Q23, and the switch tube Q21 and the switch tube Q24 are controlled to be off. The duty cycle output value DuRN is configured to be between 0 and 1.9*Period. 3.The method for uninterrupted control of a bidirectional DCDC circuit according to claim 1, characterized in that: when the bidirectional DCDC circuit works in a step-down charging mode, the switch tube Q21 and the switch tube Q24 are controlled to be always on, the switch tube Q1 is controlled to be regulated, and the switch tube Q2 is controlled to be freewheeling; when the bidirectional DCDC circuit works in a step-up charging mode, the switch tube Q1 is controlled to be always on, the switch tube Q22 and the switch tube Q23 are controlled to be regulated, and the switch tube Q21 and the switch tube Q24 are controlled to be freewheeling. ​ 2. The bidirectional DCDC circuit uninterruptible control method according to claim 1, characterized in that: ​ ​ ​ ​ When the bidirectional DCDC circuit works in the step-down discharging mode, the switch tube Q1 is always on, the switch tube Q21 and the switch tube Q24 are regulated, and the switch tube Q22 and the switch tube Q23 are freewheeling. When the bidirectional DCDC circuit works in the step-up discharging mode, the switch tube Q21 and the switch tube Q24 are always on, the switch tube Q2 is regulated, and the switch tube Q1 is freewheeling.

4. The uninterrupted control method of the bidirectional DCDC circuit according to claim 1, characterized in that: When working in any one of the step-down mode and the step-up mode, if the difference between the battery end voltage and the DC end voltage of the bidirectional DCDC circuit is within a certain range, the DC end given voltage is reduced or increased by a certain value, and then the bidirectional DCDC circuit is switched to the other mode.

5. The uninterrupted control method of the bidirectional DCDC circuit according to claim 1, characterized in that: One end of the inductor L1 is connected between the E pole of the switch tube Q1 and the C pole of the switch tube Q2, and the other end is connected between the E pole of the switch tube Q21 and the C pole of the switch tube Q22 after being connected in series with the current sensor Am1.

6. The uninterrupted control method of the bidirectional DCDC circuit according to claim 1, characterized in that: The control system architecture adopts a 1*DSP+1*FPGA mode, the two chips communicate with each other through a parallel port, and share registers; the PID algorithm is implemented in the DSP, and the calculated value is sent to the FPGA for judgment and comparison to control the corresponding switch tube.

7. The bidirectional DC-DC circuit uninterruptible control method according to claim 1, characterized by: The DC end voltage of the bidirectional DCDC circuit is less than 800V, and the highest voltage range of the battery end is greater than 1000V.

8. The bidirectional DC-DC circuit uninterruptible control method according to claim 7, characterized in that: The switch tube is configured as an IGBT.

9. The bidirectional DC-DC circuit uninterruptible control method according to claim 8, characterized in that: The upper limit of the battery end output voltage of the bidirectional DCDC circuit is configured as DC1500V, and the switch tube of the battery end of the bidirectional DCDC circuit adopts an IGBT of 1700V.

10. The bidirectional DCDC circuit uninterruptible control method according to claim 8, characterized in that: The DC end of the bidirectional DCDC circuit is configured as DC650V, and the switch tube of the DC end of the bidirectional DCDC circuit adopts an IGBT of 1200V.

11. The bidirectional DC-DC circuit uninterruptible control method according to claim 1, characterized by: The uninterrupted control method is configured to associate two independent control objects with one PID control algorithm.

12. The bidirectional DC-DC circuit uninterruptible control method according to claim 11, characterized in that: The PID control algorithm adopts a voltage outer loop plus a current inner loop, and a logic judgment is set at the PID output end.

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