Control method and system for bidirectional converter

Abstract

The present invention provides a control method and system for a bidirectional converter. The bidirectional converter includes a first switching element, and the method includes: detecting the temperature of the first switching element in real time; adjusting the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element has changed; if so, determining the temperature change trend and switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; each time the switching frequency of the first switching element is adjusted, controlling the switching action of the first switching element based on the adjusted switching frequency. The present invention can reduce costs and promptly reduce the thermal load of the bidirectional converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronics, and in particular relates to a control method and system for a bidirectional converter. Background Art

[0002] To prevent power devices in power modules from overheating and potentially failing due to continuous high-frequency operation, existing technologies employ critical conduction mode (CCM). These modules incorporate a zero-crossing detection (ZCD) circuit or current sensor, which accurately samples the voltage and current in the circuit to control the switching frequency of the power devices. However, the high cost of ZCD circuits and current sensors, coupled with the complexities of accurate sampling methods, hinders timely reduction of the thermal load on the power devices. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a control method and system for a bidirectional converter, which can reduce costs and timely reduce the thermal load of the bidirectional converter.

[0004] The present invention includes a control method for a bidirectional converter, wherein the bidirectional converter includes a first switching element, and the method includes:

[0005] detecting the temperature of the first switching element in real time;

[0006] adjusting the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element changes; if so, determining a temperature change trend and a switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend;

[0007] Each time the switching frequency of the first switching element is adjusted, the switching action of the first switching element is controlled according to the adjusted switching frequency.

[0008] Optionally, determining the temperature change trend and the switching frequency adjustment trend of the first switching element includes:

[0009] After adjusting the switching frequency of the first switching element for the kth time, comparing the temperature of the first switching element after the kth adjustment with the temperature of the first switching element after the k-1th adjustment; k≥2;

[0010] If the temperature of the first switching element after the kth adjustment is greater than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is increasing;

[0011] If the temperature of the first switching element after the kth adjustment is less than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is decreasing;

[0012] Compare the switching frequency after the kth adjustment with the switching frequency after the k-1th adjustment;

[0013] If the switching frequency after the kth adjustment is greater than the switching frequency after the k-1th adjustment, determining that the adjustment trend of the switching frequency of the first switching element is increasing;

[0014] If the switching frequency after the kth adjustment is less than the switching frequency after the k-1th adjustment, it is determined that the adjustment trend of the switching frequency of the first switching element is decreasing.

[0015] Optionally, determining the switching frequency after next adjustment according to the temperature change trend and the switching frequency adjustment trend includes:

[0016] After adjusting the switching frequency of the first switching element for the kth time, if the temperature change trend is increasing and the switching frequency adjustment trend is increasing, subtracting a preset frequency value from the switching frequency after the kth adjustment to obtain the switching frequency after the k+1th adjustment;

[0017] If the temperature change trend is increasing and the switching frequency adjustment trend is decreasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment;

[0018] If the temperature change trend is decreasing and the switching frequency adjustment trend is increasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment;

[0019] If the temperature change trend is decreasing and the switching frequency adjustment trend is decreasing, the switching frequency after the kth adjustment is subtracted from the preset frequency value to obtain the switching frequency after the k+1th adjustment.

[0020] Optionally, the method further includes:

[0021] Selecting a switching frequency from a preset switching frequency range as the switching frequency after the first adjustment;

[0022] The switching frequency after the first adjustment is added to the preset frequency value to obtain the switching frequency after the second adjustment.

[0023] Optionally, after determining the switching frequency after the next adjustment, the method further includes:

[0024] Detecting whether the switching frequency after the next adjustment is within a preset switching frequency range;

[0025] If the determined switching frequency after the next adjustment is less than the switching frequency range, re-determining the switching frequency after the next adjustment to be the minimum value of the switching frequency range;

[0026] If the determined switching frequency after the next adjustment is greater than the switching frequency range, the switching frequency after the next adjustment is re-determined to be a maximum value of the switching frequency range.

[0027] Optionally, the bidirectional converter further includes an inductor; and the method further includes:

[0028] Determining an inductance value of the inductor, an input voltage range, an output voltage, and a full load power of the bidirectional converter;

[0029] The switching frequency range is calculated according to the inductance value of the inductor, the input voltage range, the output voltage, and the full load power of the bidirectional converter.

[0030] Optionally, the calculation formula for the switching frequency range is:

[0031] Among them, f s is the switching frequency range, L is the inductance of the inductor, V LV is the input voltage of the bidirectional converter, V HV is the output voltage of the bidirectional converter, P max is the full load power of the bidirectional converter.

[0032] Optionally, the method further includes:

[0033] After adjusting the switching frequency of the first switching element for the kth time, if it is detected that the temperature of the first switching element after the kth adjustment is the same as the temperature of the first switching element after the k-1th adjustment, the switching frequency after the k+1th adjustment is determined to be the switching frequency after the k-1th adjustment.

[0034] Optionally, the bidirectional converter further includes a second switching tube, and the method further includes:

[0035] The switching action of the second switching element is controlled according to the adjusted switching frequency, so that the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0036] Accordingly, the present invention further provides a control system for a bidirectional converter, wherein the bidirectional converter includes a first switching element, and the system includes:

[0037] a temperature sensor, configured to detect the temperature of the first switching element in real time;

[0038] A processor is configured to adjust the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element has changed; if so, determining a temperature change trend and a switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; and each time the switching frequency of the first switching element is adjusted, controlling the switching action of the first switching element based on the adjusted switching frequency.

[0039] The beneficial effects of the present invention are as follows: the temperature of the first switching element in the bidirectional converter is detected in real time; the switching frequency of the first switching element is adjusted multiple times; each time the switching frequency of the first switching element is adjusted, whether the temperature of the first switching element changes is detected; if it changes, the temperature change trend and the switching frequency adjustment trend of the first switching element are determined, and the switching frequency after the next adjustment is determined according to the temperature change trend and the switching frequency adjustment trend; each time the switching frequency of the first switching element is adjusted, the switching action of the first switching element is controlled according to the adjusted switching frequency, so as to track the minimum temperature of the first switching element by adaptively adapting the optimal switching frequency, timely reduce the thermal load of the bidirectional converter, and eliminate the need to use a zero-crossing detection circuit and a current sensor, thereby reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 A schematic structural diagram of a bidirectional converter provided in an embodiment of the present application.

[0042] Figure 2a This is a waveform diagram of the bidirectional converter provided in an embodiment of the present application when there is no ZVS.

[0043] Figure 2b This is a waveform diagram of the bidirectional converter provided in an embodiment of the present application when ZVS is in effect.

[0044] Figure 3 A schematic diagram of the inductance values ​​required for the bidirectional converter in the entire load range provided in an embodiment of the present application.

[0045] Figure 4This is a current waveform diagram of the first switching element in the bidirectional converter provided in an embodiment of the present application when there is no ZVS.

[0046] Figure 5 This is a current waveform diagram of the first switching element in the bidirectional converter provided in an embodiment of the present application when ZVS is present.

[0047] Figure 6 This is a graph showing the relationship between the temperature of the first switching element and the switching frequency of the bidirectional converter provided in an embodiment of the present application under different load powers.

[0048] Figure 7 A flow chart of a control method for a bidirectional converter provided in an embodiment of the present application.

[0049] Figure 8 Another flowchart of the control method of the bidirectional converter provided in an embodiment of the present application.

[0050] Figure 9 A structural diagram of a control system of a bidirectional converter provided in an embodiment of the present application.

[0051] Figure 10 A schematic diagram of the principle of the control system of the bidirectional converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0053] An embodiment of the present invention provides a control method for a bidirectional converter. The bidirectional converter in this embodiment may be a bidirectional DC-DC (direct current-direct current) converter based on BCM (Boundary Conduction Mode), and the bidirectional converter may be widely used in various energy storage systems. Figure 1As shown, the bidirectional converter may include a first switching element S1, a second switching element S2, an inductor L, a first diode D1, a second diode D2, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a power supply V. One end of the inductor L is connected to the positive electrode of the power supply V, the other end of the inductor L is connected to the drain of the first switching element S1 and the source of the second switching element S2, the source of the first switching element S1 is connected to the negative electrode of the power supply V and one end of the third capacitor C3, and the drain of the second switching element S2 is connected to the other end of the third capacitor C3. The anode of the first diode D1 is connected to the source of the first switching element S1, the cathode of the first diode D1 is connected to the drain of the first switching element S1, and the two ends of the first capacitor C1 are connected to the source and drain of the first switching element S1, respectively. The anode of the second diode D2 is connected to the source of the second switching element S2, the cathode of the second diode D2 is connected to the drain of the second switching element S2, and the two ends of the second capacitor C2 are connected to the source and drain of the second switching element S2, respectively. The first switch element S1 and the second switch element S2 can be MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor). The voltage across the power supply V is the input voltage V of the bidirectional converter. LV The voltage across the third capacitor C3 is the output voltage V HV .

[0054] Since the first switching element S1 and the second switching element S2 work in complementary conduction, the inductive current is always continuous. min Is greater than 0, the bidirectional converter can be divided into two cases, namely I min >0, no ZVS (zero voltage switching); I min ≤0, there is ZVS. The waveforms of the bidirectional converter in two cases are as follows Figure 2a and Figure 2b As shown. Among them, V ds1 is the drain-source voltage of the first switching element S1, i L is the inductor current of the inductor L.

[0055] Input voltage V LV and the output voltage V HV It is managed by the first switching element S1 and the second switching element S2. There is a dead time between the on-time of the two switching elements for charging and discharging the inductor current. For example, during the period from t5 to t7, the voltage across the first capacitor C1 decreases, while the voltage across the second capacitor C2 increases. The drain-source voltage V ds1 The source-drain voltage V ds1 After the source-drain voltage Vds1 is set to zero, thereby forming the basis for the first switching element S1 and zero voltage switching.

[0056] As for the bidirectional converter, BCM technology is used, and the inductor is selected for energy storage to achieve zero voltage switching. During the dead time, the inductor current can be regarded as a constant current source, charging the second capacitor C2 and discharging the first capacitor C1. The energy storage of the inductor L is large enough compared to the capacitor. The minimum inductor current at t6 is I min , the dead time needs to be longer than the charging time of the second capacitor C2. In order to obtain zero voltage, the minimum inductor current I min Must be sufficiently negative, as shown below:

[0057]

[0058] Wherein, C2 is the capacitance value of the second capacitor C2, T dead is the dead time.

[0059] The inductance value of inductor L determines whether the inductor current direction can reach zero voltage. Considering the extreme operating conditions, the size of inductor L needs to meet the following conditions so that the inductor current always passes through zero.

[0060]

[0061] Wherein, D is the duty cycle of the first switching element S1, P max is the full load power of the bidirectional converter, f s-min is the minimum switching frequency of the first switching element S1.

[0062] Figure 3 shows the required inductance value for BCM over the entire load range, Figure 3 The dotted line in the figure is V HV =48V. It can be seen that when the input voltage is low, the boost inductor value is lowest due to the higher operating current. Therefore, it is necessary to design the appropriate boost inductor value at full load and the lowest input voltage.

[0063] exist Figure 1 In the circuit shown, the switching element, as the primary power device, exhibits considerable power losses. Switching element power losses primarily consist of conduction losses and switching losses. In forward power transmission, since the second switching element S2 is always turned on at zero voltage, the power device analyzed is the first switching element S1. Switching losses differ between the first switching element S1 with and without ZVS. Furthermore, switching losses are related to switching frequency, while conduction losses are a function of load current and junction temperature.

[0064] For I min >0, there is no ZVS, the current Is1 The waveform diagram is as follows Figure 4 As shown. The duty cycle D of the first switching element S1 is: T on is the on-time of the first switch element S1, T off is the off time of the first switch element S1. The current waveform △i L =Δi L =I max -I min , I max is the current I s1 The maximum value of I min is the current I s1 The average current I of the first switching element S1 is a for: T is the total duration. The integral part of this formula represents the image area enclosed by the input current I and the t-axis during the on-time of the first switching element S1. When the current flowing through the first switching element S1 in CCM mode is a trapezoidal wave, the current expression of the first switching element S1 is:

[0065] According to the definition of root mean square, we can get:

[0066]

[0067] The conduction loss of the first switching element S1 refers to the loss caused by the current in the switch resistor during the conduction time. The conduction loss is a function of the square value of the root mean square current. The conduction loss P con_CCM The calculation formula is as follows:

[0068]

[0069] Among them, R ds_on is the on-resistance. In the conduction loss estimation, the on-resistance R of the first switching element S1 is ds_on It is the main parameter related to temperature. ds_on25 is the on-resistance at a junction temperature of 25°C, which can be obtained from the datasheet. Use the on-resistance vs. junction temperature curve to approximate the ratio K ds .

[0070] Unlike conduction losses, temperature has little impact on switching losses. The switching losses of the first switching element S1 include turn-on losses and turn-off losses. When the first switching element S1 is turned on, the drain-source voltage gradually decreases, while the drain current gradually increases. This process generates an overlap, which is the switching loss of the first switching element S1. Switching losses are related to the switching frequency, the voltage across the switch, and the current through the switch.

[0071] The drain-source voltage v of the first switching element S1 ds(t) for:

[0072]

[0073] Drain-source current i ds(t) for:

[0074]

[0075] Turn-on loss P on for:

[0076]

[0077] The turn-off loss refers to the loss caused by the overlap of the drain-source voltage rise and the drain current drop during the turn-off process of the first switch element S1. ds(t) for:

[0078]

[0079] Drain-source current i ds(t) for:

[0080]

[0081] Turn-off loss P off for:

[0082]

[0083] The total loss P of the first switching element S1 loss for:

[0084] P loss =P con +P on +P off .

[0085] For I min ≤0, there is ZVS, its turn-on loss is 0, but there is turn-off loss. As long as the zero voltage is reached, the current waveform on the inductor is different, and the current flowing through the first switching element S1 is a triangular wave, such as Figure 5 shown.

[0086] The conduction loss P of the first switching element S1 con_CCM for:

[0087]

[0088] The turn-on loss P of the first switching element S1 on for:

[0089]

[0090] The turn-off loss P of the first switching element S1 off for:

[0091]

[0092] The total loss P of the first switching element S1 loss for:

[0093] P loss =P con +P on +P off .

[0094] The above analysis shows that there is a high correlation between the switching frequency and the temperature (junction temperature) of the first switching element S1. The junction temperature of the first switching element S1 is usually calculated using a thermal resistor-capacitor (RC) network. The RC network represents the equivalent heat transfer process from the chip to the heat sink and can be described by the Fourier heat conduction equation:

[0095]

[0096] The parameters of the RC model can be obtained from the cooling curve and curve fitting technology. The temperature of the first switching element S1 can be expressed as:

[0097] T j =P loss ×(Z jc +Z ch +Z ha )+T a .

[0098] Among them, P loss is the total power loss, Z jc is the thermal impedance from junction to case, Z ch is the thermal impedance between the chassis and the heat sink, Z ha The temperature T of the first switching element S1 under different load powers P is j With the switching frequency f s The curve relationship is as follows Figure 6 shown.

[0099] Based on this, Figure 7 As shown, the control method of the bidirectional converter provided by the embodiment of the present invention includes steps 101 to 103, which are specifically as follows:

[0100] Step 101: Detect the temperature of the first switching element in real time.

[0101] Combine Figure 1As shown, the first switching element is a primary power device, and its temperature fluctuates during operation. In this embodiment, a temperature sensor can be installed at the first switching element to monitor the temperature of the first switching element S1 in real time. Compared to the prior art current sensors that use thermistors for temperature detection, this embodiment uses a temperature sensor to directly monitor the temperature of the first switching element, reducing costs and effectively protecting the device.

[0102] Step 102: Adjust the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detect whether the temperature of the first switching element changes; if so, determine the temperature change trend and the switching frequency adjustment trend of the first switching element, and determine the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend.

[0103] The temperature sensor transmits the real-time detected temperature to the processor, which is equipped with an OTC (optimal temperature-based DC-DC bidirectional converter BCM adaptive frequency control) algorithm to adjust the switching frequency of the first switching element according to the detected temperature and using the OTC algorithm to ensure that the first switching element operates near the lowest temperature by disturbing the switching frequency.

[0104] First, an initial switching frequency is set for the first switching element S1, which is equivalent to adjusting the switching frequency of the first switching element S1 for the first time. Specifically, the method further includes:

[0105] Selecting a switching frequency from a preset switching frequency range as the switching frequency after the first adjustment;

[0106] The switching frequency after the first adjustment is added to the preset frequency value to obtain the switching frequency after the second adjustment.

[0107] Among them, a switching frequency can be randomly selected from the preset switching frequency range as the switching frequency f after the first adjustment s (1), the middle value of the switching frequency range can also be used as the switching frequency f after the first adjustment s (1).

[0108] Specifically, the method includes:

[0109] Determining an inductance value of the inductor, an input voltage range, an output voltage, and a full load power of the bidirectional converter;

[0110] The switching frequency range is calculated according to the inductance value of the inductor, the input voltage range, the output voltage, and the full load power of the bidirectional converter.

[0111] The calculation formula for the switching frequency range is:

[0112] Among them, f s is the switching frequency range, L is the inductance of the inductor, V LV is the input voltage of the bidirectional converter, V LV In a voltage range, V HV is the output voltage of the bidirectional converter, P max is the full load power of the bidirectional converter.

[0113] According to the first adjusted switching frequency f s (1) Control the switching action of the first switching element S1 and obtain the temperature T of the first switching element S1 after the first adjustment j (1). Then, the switching frequency of the first switching element S1 is increased, that is, the switching frequency f after the first adjustment is s Based on (1), the preset frequency Δf value is increased to obtain the switching frequency f after the second adjustment. s (2). According to the switching frequency f after the second adjustment s (2) Control the switching action of the first switching element S1 and obtain the temperature T of the first switching element S1 after the second adjustment j (2).

[0114] The second and subsequent switching frequency adjustments can be determined based on the temperature change of the first switching element. First, the temperature of the first switching element S1 is detected to determine whether it changes after each adjustment. When a temperature change is detected, the temperature change trend of the first switching element S1 and the switching frequency adjustment trend are determined. The temperature change trend refers to the temperature change of the first switching element S1 after two consecutive adjustments, and the switching frequency adjustment trend refers to the change in the switching frequency after two consecutive adjustments.

[0115] Specifically, determining the temperature change trend and the switching frequency adjustment trend of the first switching element includes:

[0116] After adjusting the switching frequency of the first switching element for the kth time, comparing the temperature of the first switching element after the kth adjustment with the temperature of the first switching element after the k-1th adjustment; k≥2;

[0117] If the temperature of the first switching element after the kth adjustment is greater than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is increasing;

[0118] If the temperature of the first switching element after the kth adjustment is less than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is decreasing;

[0119] Compare the switching frequency after the kth adjustment with the switching frequency after the k-1th adjustment;

[0120] If the switching frequency after the kth adjustment is greater than the switching frequency after the k-1th adjustment, determining that the adjustment trend of the switching frequency of the first switching element is increasing;

[0121] If the switching frequency after the kth adjustment is less than the switching frequency after the k-1th adjustment, it is determined that the adjustment trend of the switching frequency of the first switching element is decreasing.

[0122] Among them, the temperature of the first switching element S1 after the kth adjustment is T j (k), the temperature of the first switching element S1 after the k-1th adjustment is T j (k-1), ΔT j =T j (k)-T j (k-1). Determine ΔT j Is it 0? If ΔT j If it is not 0, it indicates that the temperature of the first switching element S1 has changed after the kth adjustment. j Is it greater than 0? If ΔT j >0, it indicates that the temperature change trend of the first switching element S1 after the kth adjustment is increasing; if ΔT j <0, it indicates that the temperature change trend of the first switching element S1 after the kth adjustment is decreasing.

[0123] The switching frequency after the kth adjustment is f s (k), the switching frequency f after the k-1th adjustment s (k-1). If f s (k)>f s (k-1), it indicates that after the kth adjustment, the switching frequency adjustment trend of the first switching element S1 is increasing; if f s (k)<f s (k-1), it indicates that after the kth adjustment, the switching frequency adjustment trend of the first switching element S1 is decreasing.

[0124] The determining the switching frequency after next adjustment according to the temperature change trend and the switching frequency adjustment trend includes:

[0125] After adjusting the switching frequency of the first switching element for the kth time, if the temperature change trend is increasing and the switching frequency adjustment trend is increasing, subtracting a preset frequency value from the switching frequency after the kth adjustment to obtain the switching frequency after the k+1th adjustment;

[0126] If the temperature change trend is increasing and the switching frequency adjustment trend is decreasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment;

[0127] If the temperature change trend is decreasing and the switching frequency adjustment trend is increasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment;

[0128] If the temperature change trend is decreasing and the switching frequency adjustment trend is decreasing, the switching frequency after the kth adjustment is subtracted from the preset frequency value to obtain the switching frequency after the k+1th adjustment.

[0129] like Figure 8 As shown, after the switching frequency of the first switching element S1 is adjusted for the kth time, the temperature T is detected. j (k), calculate ΔT j =T j (k)-T j (k-1). First determine ΔT j Is it 0? If ΔT j If it is not 0, further determine ΔT j Is it greater than 0? If ΔT j >0, and f s (k)≥f s (k-1), then reduce the switching frequency k+1 times, that is, the switching frequency f after the kth adjustment s (k) Subtract the preset frequency value Δf to obtain the switching frequency f after the k+1th adjustment s (k+1)=f s (k)-Δf. If ΔT j >0, and f s (k)<f s (k-1), then increase the switching frequency k+1 times, that is, the switching frequency f after the kth adjustment s (k) Add the preset frequency value Δf to get the switching frequency f after the k+1th adjustment s (k+1)=f s (k)+Δf. If ΔT j <0, and f s (k)≥f s (k-1), then the switching frequency is increased k+1 times, that is, the switching frequency f after the kth adjustment s (k) Add the preset frequency value Δf to get the switching frequency f after the k+1th adjustment s (k+1)=f s (k)+Δf. If ΔT j <0, and f s (k)<fs (k-1), then reduce the switching frequency k+1 times, that is, the switching frequency f after the kth adjustment s (k) Subtract the preset frequency value Δf to obtain the switching frequency f after the k+1th adjustment s (k+1)=f s (k)-Δf. Then, according to the switching frequency f after the k+1th adjustment, s (k+1), updating the switching frequency of the first switching element.

[0130] After determining the switching frequency after the next adjustment, it is necessary to check whether the switching frequency is within the preset switching frequency range, and then update the switching frequency of the first switching element S1. Specifically, after determining the switching frequency after the next adjustment, it also includes:

[0131] Detecting whether the switching frequency after the next adjustment is within a preset switching frequency range;

[0132] If the determined switching frequency after the next adjustment is less than the switching frequency range, re-determining the switching frequency after the next adjustment to be the minimum value of the switching frequency range;

[0133] If the determined switching frequency after the next adjustment is greater than the switching frequency range, the switching frequency after the next adjustment is re-determined to be a maximum value of the switching frequency range.

[0134] like Figure 8 As shown, after determining the switching frequency f after the k+1th adjustment s After (k+1), check f s Is (k+1) within the switching frequency range [f s_min , f s_max ], that is, f s (k+1)∈[f s_min , f s_max ]. If f s (k+1) is in the switching frequency range [f s_min , f s_max ], then based on f s (k+1) Continue to execute the subsequent step 103; if f s (k+1) is not within the switching frequency range [f s_min , f s_max ], then compare f s (k+1) and the switching frequency range [f s_min , f s_max ], if f s (k+1) is less than the switching frequency range [f s_min , f s_max ], that is, fs (k+1)<f s_min , then redetermine f s (k+1)=f s_min , and based on f s_min Continue to the subsequent step 103, if f s (k+1) is greater than the switching frequency range [f s_min , f s_max ], that is, f s (k+1)>f s_max , then redetermine f s (k+1)=f s_max , and based on f s_max Continue to execute the subsequent step 103.

[0135] After each adjustment, when detecting whether the temperature of the first switching element S1 has changed, if it is detected that the temperature of the first switching element S1 has not changed, the switching frequency of the first switching element S1 is maintained at the switching frequency after the last adjustment. Specifically, the method further includes:

[0136] After adjusting the switching frequency of the first switching element for the kth time, if it is detected that the temperature of the first switching element after the kth adjustment is the same as the temperature of the first switching element after the k-1th adjustment, the switching frequency after the k+1th adjustment is determined to be the switching frequency after the k-1th adjustment.

[0137] Among them, if ΔT j is 0, that is, T j (k) = T j (k-1), the switching frequency of the first switching element S1 is adjusted back to the switching frequency of the k-1th time, that is, the switching frequency f after the k+1th adjustment is determined. s (k+1) is the switching frequency f after the k-1th adjustment s (k-1), that is, f s (k+1)=f s (k-1).

[0138] Step 103 : Each time the switching frequency of the first switching element is adjusted, the switching action of the first switching element is controlled according to the adjusted switching frequency.

[0139] After the switching frequency of the first switching element S1 is adjusted for the kth time, the switching frequency f after the kth adjustment is adjusted. s (k) Outputting a first driving signal to the first switching element S1 to control the switching action of the first switching element S1 so that the first switching element S1 is switched according to the switching frequency f adjusted for the kth time. s (k) Turn on or off.

[0140] Furthermore, the method further comprises:

[0141] The switching action of the second switching element is controlled according to the adjusted switching frequency, so that the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0142] Since the first switch element S1 and the second switch element S2 work in complementary conduction, after the switching frequency of the first switch element S1 is adjusted for the kth time, the switching frequency f after the kth adjustment can also be adjusted. s (k) Outputting a second driving signal to the second switch element S2 to control the switching action of the second switch element S2, so that the second switch element S2 is turned off when the first switch element S1 is turned on, and the second switch element S2 is turned on when the first switch element S1 is turned off.

[0143] In summary, the present invention detects the temperature of the first switching element in the bidirectional converter in real time; adjusts the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detects whether the temperature of the first switching element changes, and if so, determines the temperature change trend and the switching frequency adjustment trend of the first switching element, and determines the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; each time the switching frequency of the first switching element is adjusted, controls the switching action of the first switching element based on the adjusted switching frequency, so as to track the minimum temperature of the first switching element through adaptive optimal switching frequency, reach zero voltage under wide load changes, timely reduce the thermal load of the bidirectional converter, and protect the energy storage system (such as the power module) from malfunctioning due to continuous high operating temperature, without the need to use a zero-crossing detection circuit and a current sensor, thereby reducing costs.

[0144] Figure 9 A schematic structural diagram of a control system of a bidirectional converter provided by this embodiment is shown. The bidirectional converter includes a first switching element. The system includes a temperature sensor 100 and a processor 200 .

[0145] a temperature sensor 100, configured to detect the temperature of the first switching element in real time;

[0146] The processor 200 is configured to adjust the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element has changed; if so, determining the temperature change trend and the switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; and each time the switching frequency of the first switching element is adjusted, controlling the switching action of the first switching element based on the adjusted switching frequency.

[0147] Combine Figure 1 and Figure 10 As shown, the temperature sensor 100 is provided at the first switching element S1 to detect the temperature T of the first switching element S1 in real time. j and the real-time detected temperature T j The processor 200 transmits the temperature T j After the OTC (DC-DC bidirectional converter BCM adaptive frequency control based on optimal temperature) algorithm, the adjusted switching frequency f is obtained. s , and determine the switching frequency f s At the same time, due to the input voltage V LV Dynamically changes within a certain range, resulting in the output voltage V HV The processor 200 also obtains the output voltage V HV and the output voltage V HV With the required voltage V ref The comparison is performed and the comparison result is passed through the PI controller (proportional integral controller) to obtain the duty cycle D of the first switching element S1. Then, the switching frequency f s The carrier Carrier and the duty cycle D are passed through the comparator to obtain the first driving signal V of the first switching element S1. gS1 and the second driving signal V of the second switching element S2 gS2 , so that the first driving signal V gS1 Control the switching action of the first switch element S1 according to the second drive signal V gS2 Control the switching action of the second switching element S2 to ensure that the first switching element S1 and the second switching element S2 are at the minimum temperature, while ensuring that the output voltage V HV Adjust to the required voltage.

[0148] The present invention detects the temperature of a first switching element in a bidirectional converter in real time; adjusts the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detects whether the temperature of the first switching element changes; if so, determines the temperature change trend and the switching frequency adjustment trend of the first switching element, and determines the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; each time the switching frequency of the first switching element is adjusted, controls the switching action of the first switching element based on the adjusted switching frequency, so as to track the minimum temperature of the first switching element through adaptive optimal switching frequency, reach zero voltage under wide load changes, timely reduce the thermal load of the bidirectional converter, and protect the energy storage system (such as a power module) from malfunctioning due to continuous high operating temperature. There is no need to use a zero-crossing detection circuit and a current sensor, thereby reducing costs.

[0149] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Within the scope of the present invention, the above embodiments or technical features in different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0150] In addition, to simplify the description and discussion, and in order not to obscure the present invention, known power / ground connections to integrated circuit (IC) chips and other components may or may not be shown in the provided figures. In addition, devices may be shown in the form of block diagrams to avoid obscuring the present invention, and this also takes into account the fact that the details of the implementation of these block diagram devices are highly dependent on the platform on which the present invention is to be implemented (i.e., these details should be fully within the scope of understanding of those skilled in the art). Where specific details (e.g., circuits) are set forth to describe exemplary embodiments of the present invention, it will be apparent to those skilled in the art that the present invention may be implemented without these specific details or with variations in these specific details. Therefore, these descriptions should be considered illustrative rather than restrictive.

[0151] Although the present invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art in light of the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may utilize the embodiments discussed.

[0152] The embodiments of the present invention are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A control method for a bidirectional converter, characterized in that: The bidirectional converter includes a first switching element, and the method includes: detecting the temperature of the first switching element in real time; adjusting the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element changes; if so, determining a temperature change trend and a switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; Each time the switching frequency of the first switching element is adjusted, the switching action of the first switching element is controlled according to the adjusted switching frequency; The determining of the temperature change trend and the switching frequency adjustment trend of the first switching element includes: After adjusting the switching frequency of the first switching element for the kth time, comparing the temperature of the first switching element after the kth adjustment with the temperature of the first switching element after the k-1th adjustment; k≥2; If the temperature of the first switching element after the kth adjustment is greater than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is increasing; If the temperature of the first switching element after the kth adjustment is less than the temperature of the first switching element after the k-1th adjustment, determining that the temperature change trend of the first switching element is decreasing; Compare the switching frequency after the kth adjustment with the switching frequency after the k-1th adjustment; If the switching frequency after the kth adjustment is greater than the switching frequency after the k-1th adjustment, determining that the adjustment trend of the switching frequency of the first switching element is increasing; If the switching frequency after the kth adjustment is less than the switching frequency after the k-1th adjustment, determining that the adjustment trend of the switching frequency of the first switching element is decreasing; The determining the switching frequency after next adjustment according to the temperature change trend and the switching frequency adjustment trend includes: After adjusting the switching frequency of the first switching element for the kth time, if the temperature change trend is increasing and the switching frequency adjustment trend is increasing, subtracting a preset frequency value from the switching frequency after the kth adjustment to obtain the switching frequency after the k+1th adjustment; If the temperature change trend is increasing and the switching frequency adjustment trend is decreasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment; If the temperature change trend is decreasing and the switching frequency adjustment trend is increasing, then the switching frequency after the kth adjustment is added to the preset frequency value to obtain the switching frequency after the k+1th adjustment; If the temperature change trend is decreasing and the switching frequency adjustment trend is decreasing, the switching frequency after the kth adjustment is subtracted from the preset frequency value to obtain the switching frequency after the k+1th adjustment.

2. The control method of the bidirectional converter according to claim 1, wherein: The method further comprises: Selecting a switching frequency from a preset switching frequency range as the switching frequency after the first adjustment; The switching frequency after the first adjustment is added to the preset frequency value to obtain the switching frequency after the second adjustment.

3. The control method of the bidirectional converter according to claim 1, wherein: After determining the switching frequency after the next adjustment, the method further includes: Detecting whether the switching frequency after the next adjustment is within a preset switching frequency range; If the determined switching frequency after the next adjustment is less than the switching frequency range, re-determining the switching frequency after the next adjustment to be the minimum value of the switching frequency range; If the determined switching frequency after the next adjustment is greater than the switching frequency range, the switching frequency after the next adjustment is re-determined to be a maximum value of the switching frequency range.

4. The control method for a bidirectional converter according to claim 2 or 3, wherein: The bidirectional converter further includes an inductor; and the method further includes: Determining an inductance value of the inductor, an input voltage range, an output voltage, and a full load power of the bidirectional converter; The switching frequency range is calculated according to the inductance value of the inductor, the input voltage range, the output voltage, and the full load power of the bidirectional converter.

5. The control method of the bidirectional converter according to claim 4, wherein: The calculation formula for the switching frequency range is: ; in, is the switching frequency range, is the inductance value of the inductor, is the input voltage of the bidirectional converter, is the output voltage of the bidirectional converter, is the full load power of the bidirectional converter.

6. The control method of the bidirectional converter according to claim 1, wherein: The method further comprises: After adjusting the switching frequency of the first switching element for the kth time, if it is detected that the temperature of the first switching element after the kth adjustment is the same as the temperature of the first switching element after the k-1th adjustment, the switching frequency after the k+1th adjustment is determined to be the switching frequency after the k-1th adjustment.

7. The control method of the bidirectional converter according to claim 1, wherein: The bidirectional converter further includes a second switching element, and the method further includes: The switching action of the second switching element is controlled according to the adjusted switching frequency, so that the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

8. A control system for a bidirectional converter implementing the method according to any one of claims 1 to 7, characterized in that: The bidirectional converter includes a first switching element, and the system includes: a temperature sensor, configured to detect the temperature of the first switching element in real time; A processor is configured to adjust the switching frequency of the first switching element multiple times; each time the switching frequency of the first switching element is adjusted, detecting whether the temperature of the first switching element has changed; if so, determining a temperature change trend and a switching frequency adjustment trend of the first switching element, and determining the switching frequency after the next adjustment based on the temperature change trend and the switching frequency adjustment trend; and each time the switching frequency of the first switching element is adjusted, controlling the switching action of the first switching element based on the adjusted switching frequency.

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