An energy storage system, liquid cooling unit and control method

Abstract

The application discloses an energy storage system, a liquid cooling unit and a control method, which can improve the reliability of the liquid cooling unit. The energy storage system comprises a liquid cooling unit and a battery pack, the liquid cooling unit is used for adjusting the temperature of the battery pack, and the liquid cooling unit comprises a three-phase driving circuit, a compressor and a controller. The three-phase driving circuit comprises a first bridge arm, a second bridge arm and a third bridge arm connected in parallel. The compressor comprises a three-phase motor, and the three-phase input end of the three-phase motor is connected with the midpoints of the first bridge arm, the second bridge arm and the third bridge arm respectively. The controller is used for controlling the upper switch tube in the second bridge arm and the lower switch tube in the third bridge arm to be simultaneously turned on for a first time length under the condition that the switch tubes in the first bridge arm are all turned off, and then controlling the lower switch tube in the second bridge arm and the lower switch tube in the third bridge arm to be simultaneously turned on. The controller is also used for controlling the liquid cooling unit to stop running when the current effective value of the second bridge arm or the third bridge arm is less than or equal to a current threshold.

Description

Technical Field

[0001] This application relates to the field of electronic power technology, and in particular to an energy storage system, a liquid cooling unit, and a control method. Background Technology

[0002] As the power density of battery packs in energy storage systems continues to increase, the packs generate more heat during operation. By controlling the operation of the three-phase motor in the liquid-cooled chiller unit to circulate the cooling medium, the temperature of the battery pack is controlled, thereby improving the safety of the energy storage system. The liquid-cooled chiller unit also includes a three-phase drive circuit, which converts direct current (DC) to three-phase alternating current (AC) to power and control the three-phase motor. If, during installation or maintenance, the physical wiring between the three-phase motor and the three-phase drive circuit becomes loose, disconnected, or has a hidden break, the power supply circuit to the three-phase motor will be interrupted, leading to a phase loss fault. This will cause the three-phase motor to malfunction, making stable operation impossible and hindering temperature control of the battery pack, thus reducing its safety.

[0003] Typically, during the operation of a three-phase motor, the three-phase current is assessed. If the current of any one phase is less than or equal to a current threshold, a phase loss fault is identified. However, during operation, if a phase loss fault exists, the current in the remaining phases will increase dramatically, causing overheating of the motor windings and triggering a three-phase motor fault. This, in turn, leads to a decrease in motor speed, resulting in vibration and abnormal noise, further increasing the risk of failure and reducing the reliability of the liquid-cooled unit. Furthermore, when the three-phase motor operates at low temperatures or speeds, the three-phase current is relatively small. Comparing the three-phase current to a single current threshold can lead to misjudgments or missed detections, further reducing the reliability of the liquid-cooled unit. Summary of the Invention

[0004] This application provides an energy storage system, a liquid chiller unit, and a control method that can improve the reliability of the liquid chiller unit.

[0005] To achieve the above objectives, the embodiments of this application adopt the following technical solutions: A first aspect of this application provides an energy storage system including a liquid-cooled chiller and a battery pack. The liquid-cooled chiller is used to regulate the temperature of the battery pack and includes a three-phase drive circuit, a compressor, and a controller. The three-phase drive circuit includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel. Each bridge arm includes an upper switch and a lower switch connected in series. The compressor includes a three-phase motor, and the three-phase input terminals of the three-phase motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm, and the third bridge arm. The controller is used to, when all the switches in the first bridge arm are off, control the upper switch in the second bridge arm and the lower switch in the third bridge arm to simultaneously turn on for a first duration, and then control the lower switch in the second bridge arm and the lower switch in the third bridge arm to simultaneously turn on, with the upper and lower switches in the second and third bridge arms being complementary in conduction. The controller is also used to control the liquid-cooled chiller to stop operating when the effective value of the current in the second or third bridge arm is less than or equal to a current threshold.

[0006] In the above technical solution, before the three-phase motor in the compressor starts, the controller controls the switching transistors in the other two phase arms to turn on and off when all the switching transistors in the first bridge arm are off, so that a current detection circuit is formed between the other two phase arms and the three-phase motor to detect phase loss in the three-phase motor. Specifically, the upper switching transistor in the second bridge arm and the lower switching transistor in the third bridge arm are controlled to be turned on simultaneously for a first duration to charge the coils of the three-phase motor and establish a stable detection current basis. Then, the lower switching transistors in the second and third bridge arms are switched on simultaneously to detect phase loss in the three-phase motor. If the effective value of the current flowing through the second or third bridge arm is less than or equal to the current threshold, it is determined that there is a phase loss fault in the three-phase motor. At this time, the liquid chiller unit is controlled to stop running to avoid discovering the phase loss fault in the three-phase motor during operation, which would further aggravate the problem of three-phase motor failure and improve the reliability of the liquid chiller unit. Furthermore, performing phase loss detection before starting the three-phase motor can avoid the problem of inaccurate phase loss detection caused by insufficient current in the three-phase motor under operating conditions such as low speed or low temperature, further improving the reliability of the liquid-cooled unit. In addition, compared with the phase loss detection method that controls the overall operation of the three-phase motor, forming a current detection loop between the two-phase bridge arm and the three-phase motor for phase loss detection simplifies the control logic of the phase loss detection process, making the detection process more stable and the judgment more accurate, avoiding interference and misjudgment introduced by complex control.

[0007] In one embodiment, the controller is further configured to, before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to conduct simultaneously for a first duration, first control the upper switch in the second bridge arm and the lower switch in the third bridge arm to conduct simultaneously for a second duration, and then control the upper switch in the second bridge arm and the upper switch in the third bridge arm to conduct simultaneously.

[0008] In the above technical solution, the control of the switching transistors in the second and third bridge arms reuses the vector control during the normal operation of the three-phase motor. This eliminates the need for additional hardware or an independent control architecture, thereby improving the reliability of phase loss detection while reducing its implementation complexity and cost. Furthermore, the turn-on time of the upper switching transistor in the second bridge arm is earlier than that in the third bridge arm, and the turn-off time is later than that in the third bridge arm. This ensures that the turn-on time of the upper switching transistor in the second bridge arm is longer than that in the third bridge arm, establishing a controlled freewheeling path for the three-phase motor coils. This avoids high-voltage spikes caused by sudden changes in coil current when the switching transistor is turned off, preventing overvoltage breakdown of the switching transistor and protecting the switching devices. This provides a stable and accurate current sampling basis for highly reliable phase loss detection.

[0009] In one implementation, within each switching cycle, the conduction time of the upper switch in the second arm and the conduction time of the upper switch in the third arm are both symmetrical about the center time of the switching cycle.

[0010] In the above technical solution, within each switching cycle, the conduction periods of the upper switching transistors in the second and third bridge arms are set to be symmetrical with respect to the center moment of the switching cycle. Furthermore, the conduction of the upper and lower switching transistors in the second and third bridge arms is complementary. By adopting a center-aligned pulse width modulation (PWM) method, the rising and falling edges of the detected current are evenly distributed on the time axis. This not only facilitates smoother and more accurate closed-loop control of the detected current and improves the signal-to-noise ratio and stability of current sampling, but also provides a more reliable data basis for subsequent phase loss judgment. Moreover, the symmetrical conduction and disconnection can optimize switching losses and improve the overall control energy efficiency and reliability.

[0011] In one embodiment, the controller is also configured to stop the liquid chiller unit from operating when the effective value of the current in the second or third bridge arm is less than or equal to a current threshold during multiple consecutive switching cycles.

[0012] In the above technical solution, the current flowing through the second and third bridge arms is continuously monitored during multiple consecutive switching cycles, and the effective value of the current in the second or third bridge arm is calculated. If the effective value of the current flowing through the second or third bridge arm is less than or equal to the current threshold during multiple switching cycles, it is determined that there is a phase loss fault in the three-phase motor. This avoids false detection of phase loss fault in the three-phase motor caused by occasional noise or sampling disturbance, thereby achieving accurate identification and reliable protection of phase loss detection and improving the robustness of the judgment.

[0013] A second aspect of this application provides a liquid-cooled unit for regulating the temperature of a battery pack. The liquid-cooled unit includes a three-phase drive circuit, a compressor, and a controller. The three-phase drive circuit includes a first arm, a second arm, and a third arm connected in parallel, each arm including an upper switch and a lower switch connected in series. The compressor includes a three-phase motor, the three-phase input terminals of which are respectively connected to the midpoints of the first arm, the second arm, and the third arm. The controller is configured to, when all switches in the first arm are off, simultaneously turn on the upper switch in the second arm and the lower switch in the third arm for a first duration, and then simultaneously turn on the lower switches in the second arm and the third arm, wherein the upper and lower switches in the second arm and the third arm are complementary in conduction. The controller is also configured to stop the liquid-cooled unit when the effective current value of the second arm or the third arm is less than or equal to a current threshold.

[0014] In one embodiment, the controller is further configured to, before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a first duration, first control the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a second duration, and then control the upper switch in the second bridge arm and the upper switch in the third bridge arm to be turned on.

[0015] In one implementation, within each switching cycle, the conduction time of the upper switch in the second arm and the conduction time of the upper switch in the third arm are both symmetrical about the center time of the switching cycle.

[0016] In one embodiment, the controller is also configured to control the liquid chiller to stop operating when the effective value of the current in the second or third bridge arm is less than or equal to a current threshold during multiple consecutive switching cycles.

[0017] A third aspect of this application provides a control method for a liquid-cooled unit, applied to a liquid-cooled unit used to regulate the temperature of a battery pack. The liquid-cooled unit includes a three-phase drive circuit and a compressor. The three-phase drive circuit includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel. Each bridge arm includes an upper switch and a lower switch connected in series. The compressor includes a three-phase motor, with the three-phase input terminals of the motor connected to the midpoints of the first bridge arm, the second bridge arm, and the third bridge arm, respectively. The method includes: when all switches in the first bridge arm are off, controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to simultaneously conduct for a first duration, then controlling the lower switch in the second bridge arm and the lower switch in the third bridge arm to simultaneously conduct, with the upper and lower switches in the second and third bridge arms conducting complementaryly, and the upper and lower switches in the third bridge arm conducting complementaryly; when the effective current value of the second or third bridge arm is less than or equal to a current threshold, controlling the liquid-cooled unit to stop operating.

[0018] In one embodiment, the method further includes: before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a first duration, controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a second duration, and then controlling the upper switch in the second bridge arm and the upper switch in the third bridge arm to be turned on.

[0019] In one implementation, within each switching cycle, the conduction time of the upper switch in the second arm and the conduction time of the upper switch in the third arm are both symmetrical about the center time of the switching cycle.

[0020] In one embodiment, the method further includes: controlling the liquid chiller unit to stop operating when the effective value of the current of the second arm or the third arm is less than or equal to a current threshold during multiple consecutive switching cycles.

[0021] The descriptions of the second and third aspects in this application can be referenced to the detailed description of the first aspect; and the beneficial effects of the second and third aspects can be referenced to the analysis of the beneficial effects of the first aspect, which will not be repeated here. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating an application scenario of an energy storage system provided in an embodiment of this application; Figure 2 A circuit topology diagram of a liquid cooling unit provided in an embodiment of this application; Figure 3 A schematic diagram of another liquid cooling unit provided in an embodiment of this application; Figure 4 A schematic diagram of the current-line curve of a liquid-cooled unit provided in an embodiment of this application; Figure 5 This is a schematic diagram of the current-line curve of another liquid-cooled unit provided in an embodiment of this application; Figure 6 This is a schematic diagram of the current-line curve of another liquid-cooled unit provided in the embodiments of this application; Figure 7 A schematic diagram illustrating the on / off timing of a switching transistor provided in an embodiment of this application; Figure 8 This is a flowchart illustrating a control method provided in an embodiment of this application. Detailed Implementation

[0023] The following sections will discuss the fabrication and use of various embodiments in detail. However, it should be understood that many applicable inventive concepts provided in this application can be implemented in a variety of specific environments. The specific embodiments discussed are merely illustrative of specific ways of implementing and using this description and technology, and do not limit the scope of this application.

[0024] Unless otherwise defined, all technical terms used herein have the same meaning as commonly known to one of ordinary skill in the art.

[0025] Each circuit or other component may be described or referred to as "for" performing one or more tasks. In this context, "for" is used to imply a structure by indicating that the circuit / component includes a structure (e.g., a circuit system) that performs one or more tasks during operation. Therefore, even when the specified circuit / component is currently inoperable (e.g., not turned on), it can still be referred to as "for performing that task." Circuits / components used with the term "for" include hardware, such as circuits that perform operations.

[0026] The technical solutions in the embodiments of this application will be described below with reference to the accompanying drawings. In this application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, a and b, a and c, b and c, or a, b, and c, where a, b, and c can be single or multiple. In addition, in the embodiments of this application, the words "first," "second," etc., do not limit the quantity or order.

[0027] In this application, the terms "first," "second," etc., do not limit the quantity or order. In this application, the words "exemplary" or "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of "exemplary" or "for example," etc., is intended to present the relevant concepts in a concrete manner.

[0028] Before introducing the embodiments of this application, the application scenarios involved in this application will be introduced first.

[0029] like Figure 1 The diagram shown illustrates an application scenario of an energy storage system 100 provided in this application embodiment. The energy storage system 100 includes a battery pack 110. The battery pack 110 can store electrical energy and release it when needed by the load, thereby achieving flexible power dispatch and economical and efficient utilization of electricity.

[0030] As the power density of the battery pack 110 in the energy storage system 100 continues to increase, the heat generated per unit time during the charging and discharging process of the battery pack 110 also increases dramatically. If a large amount of heat cannot be effectively dissipated in time, it will reduce the safety of the battery pack 110 and shorten its lifespan, thereby limiting the performance of the battery pack 110. Therefore, thermal management of the battery pack 110 is of paramount importance.

[0031] See also Figure 1 The energy storage system 100 also includes a liquid cooling unit 120. The liquid cooling unit 120 is a key component for thermal management of the battery pack 110. The liquid cooling unit 120 is used to regulate the temperature of the battery pack. Specifically, the liquid cooling unit 120 provides a cooling medium with a constant flow rate and temperature to exchange heat with the inside of the battery pack 110, thereby regulating the temperature of the battery pack 110 and ensuring that the battery pack 110 operates within a safe temperature range.

[0032] In one embodiment, such as Figure 2 The diagram shown is a circuit topology diagram of a liquid-cooled unit 120 provided in an embodiment of this application. The liquid-cooled unit 120 may include a three-phase drive circuit 121, a compressor 122, and a controller 123.

[0033] The three-phase drive circuit 121 includes a first bridge arm 1211, a second bridge arm 1212, and a third bridge arm 1213 connected in parallel. Each bridge arm includes an upper switch and a lower switch connected in series. Specifically, the second bridge arm 1212 includes an upper switch Q1 and a lower switch Q2 connected in series; the third bridge arm 1213 includes an upper switch Q3 and a lower switch Q4 connected in series; and the first bridge arm 1211 includes an upper switch Q5 and a lower switch Q6 connected in series. The connection point between the upper and lower switches in each bridge arm is the midpoint of each bridge arm. The upper switch is the switch connected to the high-potential end of the bridge arm, and the lower switch is the switch connected to the low-potential end of the bridge arm.

[0034] The compressor 122 includes a three-phase motor 1221, the three-phase input terminals of which are connected to the midpoints of the first bridge arm 1211, the second bridge arm 1212, and the third bridge arm 1213, respectively. The compressor 122 can be a liquid-cooled compressor.

[0035] The controller 123 is used to control the switching on and off of the switching transistors in the three-phase drive circuit 121, so that the three-phase drive circuit 121 converts DC power into three-phase AC power, realizes the power supply and operation control of the three-phase motor 1221, and then enables the liquid cooling unit 120 to exchange heat with the inside of the battery pack 110 by providing a cooling medium with constant flow and temperature, thereby regulating the temperature of the battery pack 110.

[0036] The aforementioned switching transistors may include metal-oxide-semiconductor field-effect transistors (MOSFETs), each MOSFET including a reverse-biased body diode. Alternatively, each switching transistor may include an insulated-gate bipolar transistor (IGBT) and a diode, with the collector of the IGBT connected to the negative terminal of the diode and the emitter of the IGBT connected to the positive terminal of the diode.

[0037] The three-phase motor 1221 is physically connected to the three-phase drive circuit 121. If the physical wiring between the three-phase motor and the three-phase drive circuit becomes loose, disconnected, or has a hidden break during installation or maintenance, the power supply circuit of the three-phase motor 1221 will be disconnected, causing a phase loss fault in the three-phase motor. This will prevent the three-phase motor 1221 from operating stably and from controlling the temperature of the battery pack 110. Consequently, the heat accumulated in the battery pack 110 will not be dissipated, potentially leading to a safety accident.

[0038] During the operation of the three-phase motor 1221, the controller 123 controls the switching transistors in the three-phase drive circuit 121 to turn them on and off. The controller 123 also checks the three-phase current of the motor 1221. If the current of any one phase is less than or equal to a current threshold, a phase loss fault is detected in the motor 1221. However, if any phase of the three-phase motor 1221 experiences a phase loss fault during operation, the current in the remaining phases will increase sharply, causing overheating of the windings and triggering a fault. This will lead to a decrease in the motor's speed, vibration, and abnormal noise, further increasing the risk of failure and reducing the reliability of the liquid-cooled unit. In addition, when the three-phase motor 1221 is operating under conditions such as low temperature or low speed, the three-phase current of the three-phase motor 1221 is relatively small. If the three-phase current is compared with a single current threshold, misjudgment or omission may occur, further reducing the reliability of the liquid cooling unit 120.

[0039] Based on this, embodiments of this application provide an energy storage system, a liquid cooling unit, and a control method. The energy storage system includes a liquid cooling unit and a battery pack. The liquid cooling unit is used to regulate the temperature of the battery pack and includes a three-phase drive circuit, a compressor, and a controller. Before starting the three-phase motor in the liquid-cooled unit, the controller, with all the switches in the first bridge arm disconnected, controls the switching of the switches in the other two bridge arms to form a current detection loop between the other two bridge arms and the three-phase motor, in order to detect phase loss in the three-phase motor. Specifically, the upper switch in the second bridge arm and the lower switch in the third bridge arm are first controlled to conduct simultaneously for a first duration to charge the coils of the three-phase motor and establish a stable detection current base. Then, the lower switch in the second bridge arm and the lower switch in the third bridge arm are switched to conduct simultaneously to detect phase loss in the three-phase motor. If the effective value of the current flowing through the second or third bridge arm is less than or equal to the current threshold, it is determined that there is a phase loss fault in the three-phase motor. At this time, the liquid-cooled unit is controlled to stop running to avoid discovering the phase loss fault in the three-phase motor during operation, which would further aggravate the problem of three-phase motor failure and improve the reliability of the liquid-cooled unit.

[0040] In one embodiment, this application provides an energy storage system 100, which includes a battery pack 110 and a liquid cooling unit 120. The liquid cooling unit 120 is used to regulate the temperature of the battery pack 110. The liquid cooling unit 120 may include a three-phase drive circuit 121, a compressor 122, and a controller 123. The circuit topology of the liquid cooling unit 120 is as described above. Figure 2 The liquid cooling unit 120 shown.

[0041] The controller 123 is configured to, when all the switches in the first bridge arm 1211 are off, simultaneously turn on the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 for a first duration, and then simultaneously turn on the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213, with the upper switch Q1 and the lower switch Q2 in the second bridge arm 1212 being complementary in conduction, and the upper switch Q3 and the lower switch Q4 in the third bridge arm 1213 being complementary in conduction. The controller 123 is also configured to stop the liquid chiller unit 120 from operating when the effective value of the current in the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to a current threshold.

[0042] The complementary conduction of the upper and lower switching transistors in the aforementioned bridge arm means that the upper and lower switching transistors operate alternately. For example, when the upper switching transistor is on, the lower switching transistor is off, and vice versa. The conduction states of the upper and lower switching transistors are always opposite and cannot be on simultaneously. This avoids the safety problem caused by a power supply short circuit due to the simultaneous conduction of the upper and lower switching transistors in the bridge arm, thus ensuring the safe and reliable operation of the three-phase drive circuit 121.

[0043] The value of the first duration is determined by the current required for the three-phase motor to perform phase loss detection. For example, the larger the required current, the larger the value of the first duration. This application does not limit this.

[0044] The aforementioned current threshold is related to the current sampling error. In an ideal situation where the current sampling error is negligible, the current threshold can be 0. However, in practical circuits, due to limitations in current sampling accuracy, noise, and non-ideal characteristics of components, a certain threshold needs to be set to avoid false triggering. For example, the current threshold can be set to 0.2 amps (A). The value of the current threshold can be determined based on the actual application scenario, sampling circuit parameters, and system sensitivity requirements; this application does not impose any limitations on this.

[0045] In one implementation, if the effective value of the current in the second bridge arm 1212 is less than or equal to the current threshold, then a phase loss fault is considered to exist in the path between the second bridge arm 1212 and the three-phase motor 1221. If the effective value of the current in the third bridge arm 1213 is less than or equal to the current threshold, then a phase loss fault is considered to exist in the path between the third bridge arm 1213 and the three-phase motor 1221.

[0046] In one implementation, see further. Figure 2 The three-phase drive circuit 121 may also include a DC bus BUS, which includes a positive DC bus BUS+ and a negative DC bus BUS-. The first bridge arm 1211, the second bridge arm 1212, and the third bridge arm 1213 are connected in parallel between the positive DC bus BUS+ and the negative DC bus BUS-. The DC bus BUS is also used to connect to the input power supply. The DC bus BUS is responsible for receiving and temporarily storing the DC power supplied by the input power supply, and providing a stable and continuous DC power input for the power conversion of the first bridge arm 1211, the second bridge arm 1212, and the third bridge arm 1213, thereby supplying power to the three-phase motor 1221 during normal operation.

[0047] In one implementation, see further. Figure 2 The three-phase drive circuit 121 may also include a bus capacitor C, which is connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. In this way, the bus capacitor C can quickly absorb or release energy, suppressing voltage pulsations and oscillations on the DC bus BUS caused by high-frequency switching of the switching transistors in the bridge arm or sudden changes in the three-phase motor 1221.

[0048] In one implementation, the three-phase motor 1221 can be a permanent magnet synchronous motor.

[0049] In one implementation, see further. Figure 2The three-phase motor 1221 includes a first coil L1, a second coil L2, and a third coil L3. The midpoint of the first bridge arm 1211 is connected to one end of the first coil L1, the midpoint of the second bridge arm 1212 is connected to one end of the second coil L2, and the midpoint of the third bridge arm 1213 is connected to one end of the third coil L3. Figure 2 The three coils of the three-phase motor 1221 are shown in a star connection as an example. However, the three coils of the three-phase motor 1221 can also be connected in a delta connection, and this application does not impose any restrictions on this. In addition, the first coil L1, the second coil L2, and the third coil L3 are the core electromagnetic components of the three-phase motor 1221. After three-phase current is applied to the three-phase motor 1221, they generate a rotating magnetic field to drive the motor rotor in the compressor 122 to rotate, thereby providing mechanical power to the compressor 122, promoting the circulation of the cooling medium, and dissipating heat for the battery pack 110.

[0050] In one implementation, such as Figure 2 As shown, the three-phase motor 1221 includes a first resistor R1, a second resistor R2, and a third resistor R3. The first resistor R1 is connected between the midpoint of the first bridge arm 1211 and one end of the first coil L1. The second resistor R2 is connected between the midpoint of the second bridge arm 1212 and one end of the second coil L2. The third resistor R3 is connected between the midpoint of the third bridge arm 1213 and one end of the third coil L3. Thus, during normal operation of the three-phase motor 1221, the controller 123 controls the switching transistors in the three-phase bridge arms to turn on and off. This converts the received current into a driving current of a certain amplitude and phase in the circuit structure where the resistors and coils are connected in series, thereby establishing a rotating magnetic field inside the three-phase motor 1221, generating electromagnetic torque, and driving the motor rotor in the compressor 122 to rotate.

[0051] In one implementation, the effective current values ​​of the second bridge arm 1212 and the third bridge arm 1213 can be calculated by detecting the current flowing through the lower switching transistor in each phase bridge arm. Since one end of the lower switching transistor is connected to the negative DC bus BUS-, its potential is more stable, allowing for direct sampling using a simple sampling circuit without complex isolation components. This reduces the difficulty of current sampling while still obtaining accurate current values. Furthermore, in the control of the three-phase motor 1221, by sampling the current during the conduction period of the lower switching transistor, the phase current waveform of the three-phase motor can be reconstructed, thereby enabling more accurate calculation of the effective current value.

[0052] In one implementation, such as Figure 3The diagram shows a circuit topology of another liquid-cooled unit 120 provided in an embodiment of this application. The liquid-cooled unit 120 may further include a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a first analog-to-digital converter (ADC1), a second conversion circuit (ADC2), and a third analog-to-digital converter (ADC3). The fourth resistor R4 is connected between the end of the lower switch Q2 in the second bridge arm 1212 furthest from the midpoint of the second bridge arm 1212 and the negative DC bus BUS-. The fifth resistor R5 is connected between the end of the lower switch Q4 in the third bridge arm 1213 furthest from the midpoint of the third bridge arm 1213 and the negative DC bus BUS-. The sixth resistor R6 is connected between the end of the lower switch Q6 in the first bridge arm 1211 furthest from the midpoint of the first bridge arm 1211 and the negative DC bus BUS-. The two input terminals of the first analog-to-digital converter (ADC1) are connected to the two ends of the fourth resistor R4, and the output terminal of the first ADC1 is connected to the controller 123. The two input terminals of the second ADC2 are connected to the two ends of the fifth resistor R5, and the output terminal of the second ADC2 is connected to the controller 123. The two input terminals of the third ADC3 are connected to the two ends of the sixth resistor R6, and the output terminal of the third ADC3 is connected to the controller 123. The fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 can be sampling resistors.

[0053] In one embodiment, the first analog-to-digital converter circuit ADC1, the second conversion circuit ADC2, and the third analog-to-digital converter circuit ADC3 may also be integrated into the controller 123, and this application does not limit this.

[0054] In this way, the analog-to-digital conversion circuit obtains the current flowing through the lower switching transistor in each phase arm by measuring the voltage drop across the sampling resistor in the path of the lower switching transistor in each phase arm, and converts the analog signal into a digital signal to feed back to the controller 123, thus providing current feedback data for the phase loss fault detection of the three-phase motor 1221. Furthermore, the sampling resistor is connected in series between the lower switching transistor in the bridge arm and the negative DC bus BUS-, making the sampling signal ground-based. This eliminates the need for complex high-voltage isolation or level shifting circuits, reducing the cost and design complexity of the sampling hardware, and improving the stability and anti-interference capability of the current measurement. This provides a more reliable and economical current detection method for the phase loss detection of the three-phase motor 1221.

[0055] In one implementation, such as Figure 4 The figure shown is a current-line diagram of a liquid-cooled unit 120 provided in an embodiment of this application. Figure 4The bold lines represent the current flow when controller 123 controls the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be turned on, and when it controls the lower switch Q2 in the second bridge arm 1212 and the upper switch Q3 in the third bridge arm 1213 to be turned off. Specifically, the current flows from the positive DC bus BUS+ through the upper switch Q1 in the second bridge arm 1212, the second resistor R2, the second coil L2, the third coil L3, the third resistor R3, the lower switch Q4 in the third bridge arm 1213, the fifth resistor R5, the negative DC bus BUS-, and the bus capacitor C back to the positive DC bus BUS+, charging the second coil L2 and the third coil L3, providing a basis for subsequent current detection.

[0056] In one implementation, such as Figure 5 The figure shown is a current-line diagram of another liquid-cooled unit 120 provided in an embodiment of this application. Figure 5 The bold lines represent the current flow direction after the coils in the three-phase motor 1221 are charged, controlling the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to conduct, and controlling the upper switch Q1 in the second bridge arm 1212 and the upper switch Q3 in the third bridge arm 1213 to disconnect. The current flows from the midpoint of the second bridge arm 1212 through the second resistor R2, the second coil L2, the third coil L3, the third resistor R3, the lower switch Q4 in the third bridge arm 1213, the fifth resistor R5, the fourth resistor R4, and the body diode of the lower switch Q2 in the second bridge arm 1212 back to the midpoint of the second bridge arm 1212. This allows the controller 123 to detect the current flowing through the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213, thus performing phase loss detection on the three-phase motor 1221. In addition, while controlling the upper switch Q1 in the second bridge arm 1212 to turn off and the lower switch Q2 in the third bridge arm 1213 to turn on, the lower switch Q4 in the third bridge arm 1213 is kept on. This can establish a controlled freewheeling path for the coil of the three-phase motor 1221, avoid the problem of overvoltage breakdown of the switch due to the sudden change in coil current when the switch is turned off, and thus protect the switching device.

[0057] In one embodiment, the three-phase drive circuit 121 includes a U-phase bridge arm, a V-phase bridge arm, and a W-phase bridge arm. The three-phase motor 1221 includes a U-coil, a V-coil, and a W-coil. In this design, the second bridge arm 1212 and the third bridge arm 1213 can be any two of the U-phase bridge arm, V-phase bridge arm, and W-phase bridge arm. The first bridge arm 1211 can be the remaining phase bridge arm among the U-phase bridge arm, V-phase bridge arm, and W-phase bridge arm, excluding the second bridge arm 1212 and the third bridge arm 1213. The second coil L2 and the third coil L3 are also coils corresponding to the phase lines of the second bridge arm 1212 and the third bridge arm 1213, respectively. The first coil L1 is the coil corresponding to the phase line of the first bridge arm 1211. For example, if the second bridge arm 1212 is the U-phase bridge arm, the third bridge arm 1213 is the V-phase bridge arm, and the first bridge arm 1211 is the W-phase bridge arm, then the second coil L2 is the U-phase coil, the third coil L3 is the V-phase coil, and the first coil L1 is the W-phase coil. This application does not impose any limitations on this.

[0058] In one embodiment, the controller 123 is further configured to control the three-phase drive circuit 121 to perform power conversion on the DC power supplied by the DC bus BUS to supply power to the three-phase motor 1221 when the current flowing through the lower switching transistors in all three-phase bridge arms is greater than the current threshold. That is, phase loss detection is performed on the paths between the U-phase and V-phase coils, the V-phase and W-phase coils, and the W-phase and U-phase coils of the three-phase motor 1221. Only after confirming that there are no phase loss faults in any of the three-phase paths of the three-phase motor 1221 is the three-phase motor 1221 controlled to operate, thereby improving the reliability of the three-phase motor 1221.

[0059] In one embodiment, the controller 123 is further configured to stop the three-phase motor 1221 from operation if the current flowing through any phase coil of the three-phase motor 1221 is less than or equal to a current threshold after the three-phase motor 1221 has started running. This continuously detects whether the three-phase motor 1221 has a phase loss fault during operation, further improving the reliability of the three-phase motor 1221.

[0060] In the energy storage system 100 provided in this application embodiment, before the three-phase motor 1221 starts, the controller 123 controls the switching transistors in the remaining two phase bridge arms to turn on and off when all the switching transistors in the first bridge arm 1211 are off, so that a current detection circuit is formed between the remaining two phase bridge arms and the three-phase motor 1221 to detect phase loss in the three-phase motor 1221. Specifically, the upper switching transistor Q1 in the second bridge arm 1212 and the lower switching transistor Q4 in the third bridge arm 1213 are simultaneously turned on for a first duration to charge the coils of the three-phase motor 1221 and establish a stable detection current. The system first switches to the second bridge arm 1212 and the third bridge arm 1213, then simultaneously turns on the lower switch Q2 and Q4 to perform phase loss detection on the three-phase motor 1221. If the effective current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to the current threshold, it is determined that the three-phase motor 1221 has a phase loss fault, and the liquid cooling unit 120 is stopped. This avoids discovering the phase loss fault in the three-phase motor 1221 during operation, thus preventing further damage to the three-phase motor 1221 and improving the reliability of the liquid cooling unit 120. Furthermore, performing phase loss detection before starting the three-phase motor 1221 also avoids inaccurate phase loss detection due to insufficient current in the three-phase motor 1221 under low speed or low temperature conditions, further improving the reliability of the variable liquid cooling unit 120. In addition, compared with the phase loss detection method that controls the overall operation of the three-phase motor 1221, the control logic of the phase loss detection process can be simplified by forming a current detection loop between the two-phase bridge arm and the three-phase motor 1221 for phase loss detection. This makes the detection process more stable and the judgment more accurate, avoiding interference and misjudgment caused by complex control.

[0061] In one embodiment, the controller 123 is further configured to, before controlling the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a first duration, first control the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a second duration, and then control the upper switch Q1 in the second bridge arm 1212 and the upper switch Q3 in the third bridge arm 1213 to be simultaneously turned on.

[0062] The basis for determining the value of the second duration is the same as that for the first duration. Referring to the above embodiments, further explanation is not required here.

[0063] In one embodiment, the controller 123 is further configured to, before simultaneously turning on the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 for a first duration, first turn on the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213, so as to refer to the current line diagram when charging the coils in the three-phase motor 1221. Figure 4 This will not be elaborated on further here.

[0064] In one implementation, such as Figure 6 The figure shown is a current-line diagram of another liquid-cooled unit 120 provided in an embodiment of this application. Figure 6 The bold lines represent the current flow direction of the controller 123 after simultaneously turning on the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 for a second duration. Specifically, the current flows from the upper switch Q1 in the second bridge arm 1212 through the midpoint of the second bridge arm 1212, the second resistor R2, the second coil L2, the third coil L3, the third resistor R3, and the body diode of the upper switch Q3 in the third bridge arm 1213 back to the upper switch Q1 in the second bridge arm 1212. This establishes a controlled freewheeling path for the coils of the three-phase motor 1221, preventing damage to the switches due to sudden current changes in the coils and thus improving the safety of the three-phase drive circuit 121.

[0065] The energy storage system 100 provided in this application uses vector control of the switching transistors in the second bridge arm 1212 and the third bridge arm 1213 during the normal operation of the three-phase motor 1221. This eliminates the need for additional hardware or an independent control architecture, thereby improving the reliability of phase loss detection while reducing its implementation complexity and cost. Furthermore, by controlling the on and off timing of the switching transistors in the second bridge arm 1212 and the third bridge arm 1213, ensuring that the on-time of the upper switching transistor Q1 in the second bridge arm 1212 is greater than that of the upper switching transistor Q3 in the third bridge arm 1213, a controlled freewheeling path can be established for the coils of the three-phase motor 1221. This avoids high-voltage spikes caused by sudden changes in coil current when the switching transistors are turned off, preventing overvoltage breakdown of the switching transistors and protecting the switching devices. This provides a stable and accurate current sampling basis for highly reliable phase loss detection.

[0066] In one implementation, such as Figure 7 This is a schematic diagram illustrating the on / off timing of a switching transistor according to an embodiment of this application. Within each switching cycle, the on-time of the upper switching transistor Q1 in the second bridge arm 1212 and the on-time of the upper switching transistor Q3 in the third bridge arm 1213 are symmetrical about the center moment of the switching cycle. Furthermore, the on-state of the upper switching transistor Q1 in the second bridge arm 1212 is complementary to the on-state of the lower switching transistor Q2, and the on-state of the upper switching transistor Q3 in the third bridge arm 1213 is complementary to the on-state of the lower switching transistor Q4. Figure 7 In the diagram, 1 represents the switch being turned on, and 0 represents the switch being turned off.

[0067] in, Figure 7The triangular carrier sequence serves as a reference signal. The count value of the triangular carrier is compared with the comparison values ​​of the second bridge arm 1212 and the third bridge arm 1213. Taking the comparison value of the second bridge arm 1212 with the triangular carrier as an example, when the count value of the triangular carrier is greater than or equal to the comparison value of the second bridge arm 1212, the upper switch Q1 in the second bridge arm 1212 is in the on state; when the count value of the triangular carrier is less than the comparison value of the second bridge arm 1212, the upper switch Q1 in the second bridge arm 1212 is in the off state. In this way, the on and off states of the switch are controlled to detect the current flowing into the switch.

[0068] To ensure precise center-aligned waveform generation and maintain high symmetry in waveform distribution over time, thus laying a solid foundation for stable operation, controller 123 also ensures accurate coordination among multiple switching transistors. Even though the conduction of the lower switching transistor Q2 in the second bridge arm 1212 and the lower switching transistor Q4 in the third bridge arm 1213 does not actually affect the detection current of the three-phase motor 1221 at the beginning of the first switching cycle, precise control of the conduction and cutoff of the lower switching transistors Q2 in the second bridge arm 1212 and Q4 in the third bridge arm 1213 is still required to achieve center-aligned waveform generation control of the switching transistors.

[0069] Furthermore, in the control logic of controller 123, when detecting the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 within multiple consecutive switching cycles, the detection of the current of the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 must be specifically avoided in the initial stage of the first switching cycle. Because in this initial stage, the current path in the circuit has not yet been fully established, and an effective current return channel has not been formed, even if the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 are in the on state, a current that truly conforms to the normal operating mode has not been formed in the circuit. Therefore, a current signal with practical analytical value cannot be detected. Avoiding detection in this stage ensures the accuracy of the acquired current data.

[0070] In one implementation, the comparison value between the second bridge arm 1212 and the third bridge arm 1213 is generated by the controller 123. Specifically, in closed-loop control, the current reference of the path between the three-phase drive circuit 121 and the three-phase motor 1221 is set to 4A. The controller 123 uses 4A as the desired reference signal and simultaneously collects the actual current of the path in real time as a feedback signal. The two are compared to obtain an error signal. Then, based on the magnitude of the error signal, the controller 123 calculates the second bridge arm 1212 and the third bridge arm 1213 through the current control loop and control algorithm, thereby realizing the control of the switching transistors in the second bridge arm 1212 and the third bridge arm 1213.

[0071] In one embodiment, the controller 123 is further configured to sample the current flowing through the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 at the moment when the count value of the triangular carrier is 0, or to sample the current flowing through the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 within a preset range at the moment when the count value of the triangular carrier is 0. The preset range refers to a symmetrical time window near the moment when the count value of the triangular carrier is 0. Thus, since the slope of the triangular carrier changes gently near the zero-crossing point (i.e., the count value is 0), the corresponding switch is usually in a stable on or off state, rather than a transient process of switching. The current ripple and switching noise are minimized during this period. Sampling the current at the moment when the count value of the triangular carrier is 0 can effectively avoid current spikes and electromagnetic interference caused by high-frequency switching of the switch, thereby capturing a stable signal reflecting the true value of the current and improving the accuracy and reliability of the sampled data.

[0072] The energy storage system 100 provided in this application embodiment sets the conduction period of the upper switch in the bridge arm to be symmetrical with respect to the center time of the switching cycle in each switching cycle, and the conduction of the upper switch and the lower switch in the bridge arm is complementary. This center-aligned PWM method makes the rising and falling edges of the detection current evenly distributed on the time axis. This not only helps to achieve smoother and more accurate closed-loop control of the detection current and improve the signal-to-noise ratio and stability of the current sampling, but also provides a more reliable data basis for subsequent phase loss judgment. Moreover, the symmetrical conduction and disconnection can also optimize switching losses and improve the overall control energy efficiency and reliability.

[0073] In one embodiment, the controller 123 is also configured to control the liquid chiller unit 120 to stop operating when the effective value of the current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to a current threshold during multiple consecutive switching cycles.

[0074] Specifically, the controller 123 is used to acquire the instantaneous current values ​​of the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 in each cycle, and to calculate the effective current values ​​of the second bridge arm 1212 and the third bridge arm 1213. If the effective current value of the second bridge arm 1212 or the third bridge arm 1213 in multiple switching cycles is less than or equal to the current threshold, then it is determined that the three-phase motor 1221 has a phase loss fault. Alternatively, the controller 123 is specifically used to acquire the instantaneous current values ​​of the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 in each cycle, and calculate the effective current values ​​of the second bridge arm 1212 and the third bridge arm 1213 based on the instantaneous current values ​​of the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 in multiple cycles. If the effective current value of the second bridge arm 1212 or the third bridge arm 1213 in multiple switching cycles is less than or equal to the current threshold, then it is determined that the three-phase motor 1221 has a phase loss fault.

[0075] The energy storage system 100 provided in this application embodiment continuously monitors the current flowing through the second bridge arm 1212 and the third bridge arm 1213 during multiple consecutive switching cycles, and calculates the effective value of the current flowing through the second bridge arm 1212 or the third bridge arm 1213. If the effective value of the current flowing through the second bridge arm or the third bridge arm is less than or equal to the current threshold during multiple switching cycles, it is determined that the three-phase motor 1221 has a phase loss fault. This avoids false detection of a phase loss fault in the three-phase motor 1221 caused by occasional noise or sampling disturbance, thereby achieving accurate identification and reliable protection of phase loss detection and improving the robustness of the judgment.

[0076] In one implementation, as described above Figure 2 As shown in the figure, this application embodiment also provides a liquid cooling unit 120, the circuit topology of which is as described above. Figures 2 to 6 The circuit topology of the liquid cooling unit 120 is shown. This liquid cooling unit 120 is used to regulate the temperature of the battery pack. The liquid cooling unit 120 may include a three-phase drive circuit 121, a compressor 122, and a controller 123.

[0077] The three-phase drive circuit 121 includes a first bridge arm 1211, a second bridge arm 1212, and a third bridge arm 1213 connected in parallel. Each bridge arm includes an upper switch and a lower switch connected in series. The compressor 122 includes a three-phase motor 1221, and the three-phase input terminals of the three-phase motor 1221 are respectively connected to the midpoints of the first bridge arm 1211, the second bridge arm 1212, and the third bridge arm 1213. The controller 123 is used to, when all the switches in the first bridge arm 1211 are off, control the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a first duration, and then control the lower switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on. The upper switch Q1 and the lower switch Q2 in the second bridge arm 1212 are complementary in conduction, and the upper switch Q3 and the lower switch Q4 in the third bridge arm 1213 are complementary in conduction. The controller 123 is also used to control the liquid chiller unit 120 to stop operating when the effective value of the current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to the current threshold.

[0078] In one embodiment, the controller 123 is further configured to, before controlling the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a first duration, first control the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a second duration, and then control the upper switch Q1 in the second bridge arm 1212 and the upper switch Q3 in the third bridge arm 1213 to be simultaneously turned on.

[0079] In one implementation, within each switching cycle, the conduction time of the upper switch Q1 in the second bridge arm 1212 and the conduction time of the upper switch Q3 in the third bridge arm 1213 are both symmetrical about the center time of the switching cycle.

[0080] In one embodiment, the controller 123 is also configured to control the liquid chiller unit 120 to stop operating when the effective value of the current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to a current threshold during multiple consecutive switching cycles.

[0081] In one implementation, such as Figure 8 The diagram shows a flow chart of a control method provided in an embodiment of this application. This control method is applied to a liquid-cooled chiller unit 120. The liquid-cooled chiller unit 120 may include a three-phase drive circuit 121 and a compressor 122. The three-phase drive circuit 121 includes a first bridge arm 1211, a second bridge arm 1212, and a third bridge arm 1213 connected in parallel. Each bridge arm includes an upper switching transistor and a lower switching transistor connected in series. The compressor 122 includes a three-phase motor 1221, and the three-phase input terminals of the three-phase motor 1221 are respectively connected to the midpoints of the first bridge arm 1211, the second bridge arm 1212, and the third bridge arm 1213. The method includes: S801, when all the switches in the first bridge arm 1211 are turned off, after controlling the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be turned on simultaneously for a first duration, the lower switch Q2 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 are turned on simultaneously.

[0082] In the second bridge arm 1212, the upper switch Q1 and the lower switch Q2 are complementaryly connected, and in the third bridge arm 1213, the upper switch Q3 and the lower switch Q4 are complementaryly connected.

[0083] S802, when the effective value of the current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to the current threshold, the liquid cooling unit 120 is controlled to stop operating.

[0084] In one embodiment, before controlling the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a first duration, the method may further include: first controlling the upper switch Q1 in the second bridge arm 1212 and the lower switch Q4 in the third bridge arm 1213 to be simultaneously turned on for a second duration, and then controlling the upper switch Q1 in the second bridge arm 1212 and the upper switch Q3 in the third bridge arm 1213 to be simultaneously turned on.

[0085] In one implementation, within each switching cycle, the conduction time of the upper switch Q1 in the second bridge arm 1212 and the conduction time of the upper switch Q3 in the third bridge arm 1213 are both symmetrical about the center time of the switching cycle.

[0086] In one implementation, reference Figure 8 If the effective current value of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to the current threshold, the remaining phases of the three-phase motor 1221 are detected. If there is no missing phase in the remaining phases, the three-phase motor 1221 is controlled to start.

[0087] In one embodiment, the method may further include: controlling the liquid cooling unit 120 to stop operating when the effective value of the current of the second bridge arm 1212 or the third bridge arm 1213 is less than or equal to a current threshold during multiple consecutive switching cycles.

[0088] The above detailed description of the energy storage system 100 and the analysis of its beneficial effects can be applied to the liquid cooling unit 120 and the control method, and will not be repeated here in the embodiments of this application.

[0089] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be covered within the scope of protection of this application.

Claims

1. An energy storage system, characterized in that, It includes a liquid cooling unit and a battery pack, wherein the liquid cooling unit is used to regulate the temperature of the battery pack, and the liquid cooling unit includes a three-phase drive circuit, a compressor and a controller; The three-phase drive circuit includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel, and each bridge arm includes an upper switch and a lower switch connected in series. The compressor includes a three-phase motor, and the three-phase input terminals of the three-phase motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm and the third bridge arm; The controller is configured to, when all the switches in the first bridge arm are off, simultaneously turn on the upper switch in the second bridge arm and the lower switch in the third bridge arm for a first duration, and then simultaneously turn on the lower switch in the second bridge arm and the lower switch in the third bridge arm, wherein the upper switch in the second bridge arm and the lower switch in the third bridge arm are complementaryly turned on, and the upper switch in the third bridge arm and the lower switch in the third bridge arm are complementaryly turned on. The controller is also used to control the liquid cooling unit to stop operating when the effective value of the current in the second or third bridge arm is less than or equal to the current threshold.

2. The energy storage system according to claim 1, characterized in that, The controller is further configured to, before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a first duration, first control the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a second duration, and then control the upper switch in the second bridge arm and the upper switch in the third bridge arm to be simultaneously turned on.

3. The energy storage system according to claim 1 or 2, characterized in that, Within each switching cycle, the conduction time of the upper switch in the second bridge arm and the conduction time of the upper switch in the third bridge arm are both symmetrical about the center time of the switching cycle.

4. The energy storage system according to claim 3, characterized in that, The controller is also configured to control the liquid cooling unit to stop operating when the effective current value of the second or third bridge arm is less than or equal to the current threshold during multiple consecutive switching cycles.

5. A liquid-cooled unit, characterized in that, The liquid cooling unit is used to regulate the temperature of the battery pack; the liquid cooling unit includes a three-phase drive circuit, a compressor, and a controller; The three-phase drive circuit includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel, and each bridge arm includes an upper switch and a lower switch connected in series. The compressor includes a three-phase motor, and the three-phase input terminals of the three-phase motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm and the third bridge arm; The controller is configured to, when all the switches in the first bridge arm are off, simultaneously turn on the upper switch in the second bridge arm and the lower switch in the third bridge arm for a first duration, and then simultaneously turn on the lower switch in the second bridge arm and the lower switch in the third bridge arm, wherein the upper switch in the second bridge arm and the lower switch in the third bridge arm are complementaryly turned on, and the upper switch in the third bridge arm and the lower switch in the third bridge arm are complementaryly turned on. The controller is also used to control the liquid cooling unit to stop operating when the effective value of the current in the second or third bridge arm is less than or equal to the current threshold.

6. The liquid-cooled unit according to claim 5, characterized in that, The controller is further configured to, before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a first duration, first control the upper switch in the second bridge arm and the lower switch in the third bridge arm to be simultaneously turned on for a second duration, and then control the upper switch in the second bridge arm and the upper switch in the third bridge arm to be turned on.

7. The liquid-cooled unit according to claim 5 or 6, characterized in that, Within each switching cycle, the conduction time of the upper switch in the second bridge arm and the conduction time of the upper switch in the third bridge arm are both symmetrical about the center time of the switching cycle.

8. The liquid-cooled unit according to claim 7, characterized in that, The controller is also configured to control the liquid cooling unit to stop operating when the effective current value of the second or third bridge arm is less than or equal to the current threshold during multiple consecutive switching cycles.

9. A control method for a liquid-cooled unit, characterized in that, This invention is applied to a liquid cooling unit used to regulate the temperature of a battery pack. The liquid cooling unit includes a three-phase drive circuit and a compressor. The three-phase drive circuit includes a first bridge arm, a second bridge arm, and a third bridge arm connected in parallel. Each bridge arm includes an upper switch and a lower switch connected in series. The compressor includes a three-phase motor. The three-phase input terminals of the three-phase motor are respectively connected to the midpoints of the first bridge arm, the second bridge arm, and the third bridge arm. When all the switches in the first bridge arm are turned off, after controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to be turned on simultaneously for a first duration, the lower switch in the second bridge arm and the lower switch in the third bridge arm are turned on simultaneously, with the upper and lower switches in the second bridge arm being complementaryly turned on, and the upper and lower switches in the third bridge arm being complementaryly turned on. When the effective value of the current in the second or third bridge arm is less than or equal to the current threshold, the liquid cooling unit is controlled to stop operating.

10. The method according to claim 9, characterized in that, The method further includes: Before controlling the upper switch in the second bridge arm and the lower switch in the third bridge arm to conduct simultaneously for a first duration, first control the upper switch in the second bridge arm and the lower switch in the third bridge arm to conduct simultaneously for a second duration, and then control the upper switch in the second bridge arm and the upper switch in the third bridge arm to conduct.

11. The method according to claim 9 or 10, characterized in that, Within each switching cycle, the conduction time of the upper switch in the second bridge arm and the conduction time of the upper switch in the third bridge arm are both symmetrical about the center time of the switching cycle.

12. The method according to claim 11, characterized in that, The method further includes: During multiple consecutive switching cycles, when the effective current value of the second or third bridge arm is less than or equal to the current threshold, the liquid cooling unit is controlled to stop operating.

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