A slice type direct charging device without pfc / boost and method

Abstract

This invention relates to a PFC / Boost-free slice-type direct charging method, comprising the following steps: Step 1. Setting the AC / DC rectifier to operate in a state where it charges a DC power source using AC power; Step 2. Adjusting the switching network state of the DC power source based on the instantaneous voltage value of the AC power source; Step 3. Repeating Step 2 in each half-wave cycle of the AC power supply. This invention also discloses a PFC / Boost-free slice-type direct charging device. The PFC / Boost-free slice-type direct charging device and method of this invention eliminate high-frequency PWM losses by algorithmically slicing and distributing charging pulses, thereby eliminating dependence on bulky PFC, Boost circuits, and large LC filters, and achieving extremely high-efficiency low-frequency direct charging and dynamic battery power balancing.

Description

Technical Field

[0001] This invention belongs to the field of battery energy storage technology and relates to Dynamic Reconfiguration Battery Converter (DRBC) technology, specifically a slice-type direct charging device and method without PFC / Boost. Background Technology

[0002] In existing battery energy storage systems and electric vehicle charging technologies, AC-to-DC charging commonly employs a traditional high-frequency PWM inverter architecture. This architecture mainly suffers from the following problems: 1. High losses due to multi-stage conversion: Traditional charging solutions typically require multiple conversion stages: AC grid → step-up transformer → PFC correction / high-frequency rectification → high-voltage DC-DC step-down / regulation → battery. Switching frequencies exceeding 20kHz generate significant switching losses (typical single-unit losses exceeding 40W), necessitating large cooling fans and producing severe noise.

[0003] 2. Large system size and complex topology: To deal with high-frequency harmonics and EMI problems, traditional solutions rely on bulky LC or LCL filters (which usually account for a large proportion of the overall system size), which increases the system cost.

[0004] 3. Battery balancing is independent of charging: Traditional battery packs have a fixed series structure, which leads to the "weakest link" effect. During charging, a high voltage must be applied to the entire battery pack, making it impossible to perform dynamic energy distribution based on the differences in SOC (State of Charge) of individual cells / modules from a charging perspective.

[0005] 4. Conventional charging modes affect battery life: Although current CC-CV fast charging can improve the charging rate, it will accelerate the deposition of negative electrode lithium and SEI growth, resulting in rapid capacity decay. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, this invention discloses a PFC / Boost-free slice-type direct charging device and method.

[0007] This invention discloses a PFC / Boost-free slice-type direct charging method, comprising the following steps: Step 1. Set the AC / DC rectifier to charge the DC power supply using AC power; so that the AC / DC rectifier continuously outputs a DC voltage with a value greater than zero. Step 2. Adjust the switching network state of the DC power supply according to the instantaneous voltage value of the AC power supply; specifically: Step 21. Collect the instantaneous AC voltage value of the current AC power supply, as well as the instantaneous voltage value and battery parameters of each battery; Step 22. Combine the instantaneous voltage values ​​of each battery in different ways to obtain multiple instantaneous DC voltage sums. When the difference between the instantaneous AC voltage value and a certain instantaneous DC voltage sum is greater than zero and less than a set first voltage difference threshold, adjust the switching network so that each battery corresponding to that instantaneous DC voltage sum is connected. Step 23. When the difference between the instantaneous AC voltage value and the instantaneous DC voltage is less than zero or greater than the set first voltage difference threshold, the previously connected battery is disconnected and the process returns to step 22. Step 3. Repeat step 2 for each half-wave cycle of the alternating current.

[0008] Preferably, in step 22, when the instantaneous DC voltage and voltage are combined, for multiple access methods with the same number of batteries connected, only the method with the lowest remaining battery power is selected.

[0009] Preferably, the battery power comprehensive parameter SAL is set as SOC*SOH. For multiple access methods with the same number of batteries, when selecting a battery, the battery or battery combination with the lowest battery power comprehensive parameter SAL is selected first. When the battery power comprehensive parameter SAL of different methods is equal, the battery with the lower temperature is selected first. Where SOC is the remaining battery power and SOH is the battery health status.

[0010] Preferably, in step 21, if the instantaneous voltage value or battery parameters of a certain battery are abnormal, the battery is not considered in subsequent steps, and the switching network is adjusted so that the battery is not connected.

[0011] A PFC / Boost-free slice-type direct charging device includes multiple battery units. Each battery unit includes a battery. The first electrode and the second electrode of the battery are respectively connected to a first switch and a second switch. The ends of the first switch and the second switch that are not connected to the electrodes are connected together as the bottom end of the battery unit. The first electrode or the second electrode serves as the top end of the battery unit. The bottom of each battery cell is connected to the top of the adjacent battery cell to form a battery cell string. The top of the first battery cell and the bottom of the last battery cell are respectively connected to the two DC terminals of an AC / DC rectifier. The two AC terminals of the AC / DC rectifier are connected to an AC power source. The direct charging device also includes a voltage detection module and a switch control device. The voltage detection module is used to detect the AC power source parameters and the battery parameters of each battery cell. The switch control device adjusts the switch states according to the detection results of the voltage detection device.

[0012] Preferably, the battery uses standardized battery modules, and each battery module has a built-in independent battery management unit.

[0013] Preferably, the AC / DC converter uses a full-bridge rectifier circuit composed of four switching transistors.

[0014] Preferably, the first switch and the second switch are implemented as follows: a first switch and a second switch are connected in series, the control terminals of the two switches are connected together as the switch control terminals, the drains of the two switches are respectively used as the input and output terminals of the switch, and the sources are connected together and connected to the substrate.

[0015] Preferably, a filter consisting of an inductor and a capacitor is connected between the output terminal of the AC-DC converter and the AC power supply.

[0016] The PFC / Boost-free slice-type direct charging device and method of the present invention eliminates high-frequency PWM loss by slicing charging pulses through algorithm, thereby getting rid of the dependence on bulky PFC, Boost circuits and large LC filters, and can achieve extremely efficient low-frequency direct charging and dynamic battery power balancing. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a specific implementation of the slice-type direct charging method described in this invention; Figure 2 This is a schematic diagram of a specific embodiment of the slice-type direct charging device described in this invention; Figure 3 This is a schematic diagram of a specific implementation of step 2 of the slice-type direct charging method based on the present invention; Figure 4 This is a schematic diagram of a specific embodiment of the switch based on the present invention; The labels in the diagram are as follows: L - inductor, CW - filter capacitor, K1 - first switch, K2 - second switch, BMS - battery management unit, AC - AC power supply, M1 - first switch, M2 - second switch. Detailed Implementation

[0018] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0019] The PFC / Boost-free slice-type direct charging method described in this invention is applied to mutual charging between AC power supply and DC power supply using AC / DC rectifiers. The DC power supply is composed of multiple batteries connected in series and includes a switching network that allows any battery to be connected to or not connected to the battery string.

[0020] The PFC / Boost-free slice-type direct charging method of the present invention specifically includes the following steps: Step 1. Based on the operating status, set the AC / DC rectifier to charge the DC power supply using AC power. In step 1, when the working state is charging from AC power to DC power, the AC / DC rectifier is set to reverse polarity only when the AC voltage crosses zero, so that the AC / DC rectifier continuously outputs a half-wave DC voltage with a voltage value greater than zero; the AC / DC converter can use a full-bridge rectifier circuit composed of four switching transistors.

[0021] Step 2. This step is used to charge the battery using AC power. The switching network state of the DC power supply is adjusted according to the instantaneous AC voltage value of the AC power supply. In this invention, the AC power output by the AC power source is a sinusoidal waveform, and the instantaneous AC voltage value of the AC power source is the current voltage of the sinusoidal waveform.

[0022] Step 2 of this invention specifically includes: Step 21. Collect the instantaneous AC voltage value of the current AC power supply, as well as the instantaneous voltage value and battery parameters of each battery; When collecting instantaneous voltage values ​​and battery parameters, data can be collected and updated at the start of the entire AC cycle, or at the start and midpoint of a half-cycle of the AC cycle. In this step, if the instantaneous voltage value or battery parameters of a certain battery are abnormal, such as abnormally low voltage or abnormally high temperature, the battery is considered to be faulty. In subsequent steps, the various instantaneous DC voltages of the battery will no longer be considered, and the switching network will be adjusted so that the battery is not connected.

[0023] Step 22. Combine the instantaneous voltage values ​​of each battery in different ways to obtain multiple instantaneous DC voltage sums. When the difference between the instantaneous AC voltage value and a certain instantaneous DC voltage sum is greater than zero and less than a set first voltage difference threshold, adjust the switching network so that each battery corresponding to that instantaneous DC voltage sum is connected. Step 23. When the difference between the instantaneous AC voltage value and the instantaneous DC voltage is less than zero or greater than the set first voltage difference threshold, the previously connected battery is disconnected and the process returns to step 22. Alternating current waveforms are periodically arranged sine waves, divided into rising and falling phases; During the AC voltage rise phase, when the difference between the instantaneous AC voltage and the sum of the instantaneous DC voltages exceeds the set first voltage difference threshold, it is no longer suitable to use the currently selected sum of instantaneous DC voltages. The switching network needs to be adjusted, and the process should be restarted in step 22. During the AC voltage drop phase, when the instantaneous AC voltage is lower than the instantaneous DC voltage selected in step 22, it is no longer possible to use AC to charge the battery voltage which is higher than its own voltage. The switching network needs to be adjusted and the process needs to re-enter step 22. Taking a DC power supply using a three-battery combination as an example, assuming that the voltage of each battery is constant, the voltages of the three batteries C1, C2, and C3 are 90V, 100V, and 105V respectively; there are a total of seven possible values ​​for the instantaneous DC voltage when only one battery is connected, or when two or three batteries are connected at the same time, namely 90, 100, 105, 190, 195, 205, and 295; the first voltage difference threshold is set to 2V.

[0024] When the instantaneous AC voltage value of the AC power supply rises above 90V at a certain point in the rising phase of the AC power supply waveform, the instantaneous DC voltage of 90V meets the judgment condition of step 22, and the battery C1 is connected, and the AC power starts to charge the battery C1. When the AC voltage continues to rise to 92V, the difference between it and 90V is greater than the first voltage difference threshold. At this point, battery C1 is disconnected, and the AC voltage stops charging battery C1. When the AC voltage continues to rise to 100V, the difference between it and 100V is less than the first voltage difference threshold. At this point, battery C2 is connected, and the AC voltage starts charging battery C2. And so on. In the AC voltage drop region, when the AC voltage drops from its peak to 297V, it meets the judgment condition of step 22 compared to the voltage of 295V when all three batteries are connected at the same time. Therefore, all batteries C1, C2 and C3 are connected, and the AC power begins to charge all batteries at the same time. When the AC voltage continues to drop below 295V, the connected batteries are disconnected. When the AC voltage continues to drop to 207V, the voltage of 205V at this point meets the judgment condition. Connect batteries C2 and C3, and the AC power will charge batteries C2 and C3, and so on.

[0025] In practice, when multiple connection methods are available for the same number of batteries, only the method with the lowest remaining battery power is selected. For example, if the remaining battery power is C1, C2, and C3 from lowest to highest, then when connecting a single battery, only C1 is selected; when connecting two batteries, only C1 and C2 are selected. This principle continues for more batteries. Figure 3 As shown, during one half-wave cycle of AC power, the connected batteries are C1, C1+C2 and C1+C2+C3, respectively.

[0026] The remaining power of each battery can be estimated in real time based on Kalman filtering. In a preferred embodiment, the battery with the lowest remaining power is selected for charging first. For example, suppose the voltages of the three batteries C1, C2, and C3 are 90V, 100V, and 105V, respectively; but battery C1 has the lowest remaining power. In this case, the instantaneous DC voltage sum is set to only consider the case where battery C1 is connected. There are only four possible instantaneous DC voltage sums: C1 connected, C1 and C2 connected, C1 and C3 connected, and all three batteries connected. The corresponding instantaneous DC voltage sums are 90, 190, 195, and 295V, respectively.

[0027] Furthermore, when only two batteries are connected, when choosing between C2 and C3, the battery with the smaller remaining charge is preferred.

[0028] In a preferred embodiment, the following factors are considered when selecting which batteries to connect: battery remaining charge (SOC), battery health (SOH), and battery temperature (T). Battery health characterizes the battery's capacity to hold.

[0029] Set the battery power comprehensive parameter SAL=SOC*SOH. For multiple selectable access methods with the same number of batteries, when selecting a battery, first select the battery or battery combination with the lowest battery power comprehensive parameter SAL. When the battery power comprehensive parameter SAL of different methods is equal, prioritize the battery with the lower temperature.

[0030] For example, the SOCs of three batteries C1, C2, and C3 are 0.7, 0.8, and 1, respectively; the SOHs of the three batteries are 0.5, 0.4, and 0.4, respectively; and the SALs of the three batteries are 0.35, 0.4, and 0.4, respectively. When connecting one battery, C1 is preferred. When connecting two batteries, since C2 and C3 have the same SAL value, their temperatures are compared, and the battery with the lower temperature is selected.

[0031] Step 3. Repeat step 2 for each half-wave cycle of the alternating current.

[0032] Compared with the prior art, the present invention has the following technical advantages: 1. Eliminate high-frequency loss and improve efficiency: This invention abandons the traditional 20kHz high-frequency PWM modulation and instead uses 50Hz power frequency reverse rectification and NLC stepped wave approximation. The switching loss is greatly reduced from about 40W to about 2W. The overall direct charging efficiency of the system, including AC-DC conversion and charging management, can reach 98.8%.

[0033] 2. Reduced hardware size: This invention eliminates the need for traditional PFC boost inductors, large-capacity energy storage capacitors, and boost circuits. The size of the filter circuit used is reduced to 1 / 10 of the traditional size to meet grid connection and absorption requirements.

[0034] 3. Deep integration of charging and active balancing: During the waveform slice absorption process in each cycle, the low complexity of the control algorithm achieves nanosecond-level fast response, enabling activation time redistribution every 100ms or even shorter cycles. Simultaneously, low-SOC modules are prioritized for charging, increasing usable capacity by 15-20%.

[0035] 4. Built-in module-level hardware-level fault isolation: When a single battery module fails, the battery module is quickly isolated through the switching network. The system only needs to perform corresponding derating operation instead of shutting down completely. The charging process will not stop the entire machine due to the failure of a single cell.

[0036] The PFC / Boost-free slice-type direct charging device described in this invention, such as... Figure 2 As shown, it includes multiple battery units, each battery unit includes a battery, the first electrode and the second electrode of the battery are respectively connected to the first switch K1 and the second switch K2, the ends of the first switch and the second switch that are not connected to the electrodes are connected together as the bottom end of the battery unit, and the first electrode or the second electrode serves as the top end of the battery unit. The bottom of each battery cell is connected to the top of the adjacent battery cell to form a battery cell string. The top of the first battery cell and the bottom of the last battery cell are respectively connected to the two DC terminals of an AC / DC rectifier. The two AC terminals of the AC / DC rectifier are connected to an AC power supply. The direct charging device also includes a voltage detection module and a switch control device. The voltage detection module is used to detect the AC power supply parameters and the battery parameters of each battery cell. The switch control device adjusts the state of each switch according to the detection results of the voltage detection device.

[0037] The battery can be a standardized battery module, such as a 36S / 52S lithium iron phosphate battery module. Each battery module has a built-in independent battery management unit (BMS). The BMS is used to manage the power of the battery module and detect its voltage, remaining state of charge (SOC), state of health (SOH), and temperature. The BMS is connected to the voltage detection module and sends the detected parameters to the voltage detection module.

[0038] The PFC / Boost-free slice-type direct charging device is used to implement the slice-type direct charging method of the present invention. It can also be used to convert DC power to AC power, but the specific method of DC to AC conversion is not involved in the present invention and will not be described here.

[0039] like Figure 2In the specific embodiment shown, the AC / DC converter can employ a full-bridge rectifier circuit D4 composed of four switching transistors. By controlling the switching states of the four switching transistors in D4, the polarity is reversed when the AC voltage crosses zero, resulting in a continuous output of a half-wave DC voltage with a voltage value greater than zero at the output terminal. The timing logic control of the four switches is prior art and will not be described in detail here.

[0040] When battery C1 needs to be connected, close the first switch K1 connected to C1 and open the second switch C2 connected to C1. When battery C1 is not needed, open the first switch K1 and close the second switch K2. The same applies to other batteries C2 and C3.

[0041] For example, if only C1 needs to be connected, then close the first switch K1 connected to C1, open the second switch C2 connected to C1, open the first switch K1 connecting C2 and C3 at the same time, and close the second switch K2 connecting C2 and C3.

[0042] When only C1 and C2 need to be connected, close the first switch K1 connecting C1 and C2, open the second switch C2 connecting C1 and C2, open the first switch K1 connecting C3, and close the second switch K2 connecting C3.

[0043] When C1, C2, and C3 need to be connected simultaneously, all first switches K1 are closed and all second switches C2 are opened.

[0044] Figure 2 In the specific embodiment shown, a filter consisting of an inductor L and a capacitor CW is connected between the output terminal of the AC-DC converter and the AC power supply AC for filtering.

[0045] A specific implementation method for each switch is as follows: Figure 4 As shown, the circuit includes a first switch M1 and a second switch M2 connected in series. The control terminals of the two switches are connected together as the switch control terminals. The drains of the two switches serve as the input and output terminals of the switch, respectively, and their sources are connected together and connected to the substrate. The two switches are typically NMOS transistors with higher conductivity. For example, using an NMOS transistor... Figure 4 As shown, for an NMOS transistor, there exists a parasitic diode DS pointing from the substrate to the drain. If only one NMOS transistor is used, in Figure 4 In the circuit, if the voltage on the left side is low, the current can flow directly through the parasitic diode of the first switching transistor M1. At this time, whether the gate voltage of the first switching transistor is high or low, it will not affect the conduction of the parasitic diode, causing the circuit to fail. However, when two NMOS transistors are connected in series, the parasitic diodes of the two NMOS transistors are connected back to back. When the channel is not formed, one of the two parasitic diodes will be conducting and the other will be closed, so that when the switch is closed, there will be no leakage current due to the parasitic diode.

[0046] The foregoing descriptions are preferred embodiments of the present invention. Unless there is a clear contradiction between the preferred embodiments or a prerequisite for a particular preferred embodiment, the preferred embodiments can be arbitrarily combined and used. The embodiments and specific parameters described are only for clearly illustrating the inventor's invention verification process and are not intended to limit the scope of patent protection of the present invention. The scope of patent protection of the present invention shall still be determined by its claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A PFC / Boost-free slice-type direct charging method, characterized in that, Includes the following steps: Step 1. Set the AC / DC rectifier to charge the DC power supply using AC power; so that the AC / DC rectifier continuously outputs a DC voltage with a value greater than zero. Step 2. Adjust the switching network state of the DC power supply according to the instantaneous voltage value of the AC power supply; specifically: Step 21. Collect the instantaneous AC voltage value of the current AC power supply, as well as the instantaneous voltage value and battery parameters of each battery; Step 22. Combine the instantaneous voltage values ​​of each battery in different ways to obtain multiple instantaneous DC voltage sums. When the difference between the instantaneous AC voltage value and a certain instantaneous DC voltage sum is greater than zero and less than a set first voltage difference threshold, adjust the switching network so that each battery corresponding to that instantaneous DC voltage sum is connected. Step 23. When the difference between the instantaneous AC voltage value and the instantaneous DC voltage is less than zero or greater than the set first voltage difference threshold, the previously connected battery is disconnected and the process returns to step 22. Step 3. Repeat step 2 for each half-wave cycle of the alternating current.

2. The slice-type direct charging method as described in claim 1, characterized in that, In step 22, when the instantaneous DC voltage and time are obtained by combining them, for multiple access methods with the same number of batteries connected, only the method with the lowest remaining battery power is selected.

3. The slice-type direct charging method as described in claim 1, characterized in that, Set the battery power comprehensive parameter SAL=SOC*SOH. For multiple access methods with the same number of batteries, when selecting a battery, first select the battery or battery combination with the lowest battery power comprehensive parameter SAL. When the battery power comprehensive parameter SAL of different methods is equal, prioritize the battery with the lower temperature. Where SOC is the remaining battery power and SOH is the battery health status.

4. The slice-type direct charging method as described in claim 1, characterized in that, In step 21, if the instantaneous voltage value or battery parameters of a certain battery are abnormal, the battery will not be considered in subsequent steps, and the switching network will be adjusted so that the battery is not connected.

5. A slice-type direct charging device without PFC / Boost, characterized in that, It includes multiple battery units, each battery unit includes a battery, the first electrode and the second electrode of the battery are respectively connected to a first switch and a second switch, the ends of the first switch and the second switch that are not connected to the electrodes are connected together as the bottom end of the battery unit, and the first electrode or the second electrode serves as the top end of the battery unit. The bottom of each battery cell is connected to the top of the adjacent battery cell to form a battery cell string. The top of the first battery cell and the bottom of the last battery cell are respectively connected to the two DC terminals of an AC / DC rectifier. The two AC terminals of the AC / DC rectifier are connected to an AC power source. The direct charging device also includes a voltage detection module and a switch control device. The voltage detection module is used to detect the AC power source parameters and the battery parameters of each battery cell. The switch control device adjusts the switch states according to the detection results of the voltage detection device.

6. The slice-type direct charging device as described in claim 5, characterized in that, The battery uses standardized battery modules, and each battery module has an independent built-in battery management unit.

7. The slice-type direct charging device as described in claim 5, characterized in that, The AC / DC converter uses a full-bridge rectifier circuit composed of four switching transistors.

8. The slice-type direct charging device as described in claim 5, characterized in that, The first and second switches are implemented as follows: they include a first switch and a second switch connected in series. The control terminals of the two switches are connected together as the switch control terminals. The drains of the two switches are respectively used as the input and output terminals of the switch. The sources are connected together and connected to the substrate.

9. The slice-type direct charging device as described in claim 5, characterized in that, A filter consisting of an inductor and a capacitor is connected between the output of the AC-DC converter and the AC power supply.

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