System and method for reducing dc bus capacitor ripple current
By introducing an energy storage inductor and control circuit into the DC bus capacitor system, the ripple current is reduced, the problem of capacitor temperature rise is solved, the capacitor life is extended, and the cost is reduced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YINCHUAN WEILI REDUCER MACHINERY
- Filing Date
- 2023-11-24
- Publication Date
- 2026-07-03
Smart Images
Figure CN117614255B_ABST
Abstract
Description
[Technical Field]
[0001] This invention relates to the field of current control technology, and in particular to a system and method for reducing DC bus capacitor ripple current that is simple in structure and can effectively reduce capacitor temperature rise and extend capacitor life. [Background Technology]
[0002] With the rapid development of new energy vehicles, the power requirements of motor controllers are increasing, leading to a significant increase in the ripple current of the DC bus capacitors inside the controllers. The higher the ripple current the capacitors bear, the higher the temperature rise during operation, which in turn reduces their lifespan. Currently, the market mainly uses indirect heat dissipation of the capacitors through the controller casing to ensure the bus capacitors can withstand the ripple current generated by the controller, or by increasing the number of capacitor cores to reduce the ripple current borne by each individual core, thereby reducing the heat generated by each core and lowering the overall temperature rise of the capacitor. However, increasing the number of capacitor cores increases the size and cost of the capacitor. Therefore, providing a method to effectively reduce the ripple current of the DC bus capacitors at a low cost has become an objective requirement. [Summary of the Invention]
[0003] The present invention aims to solve the above problems and provides a low-cost, simple-structure, and highly reliable system for reducing DC bus capacitor ripple current.
[0004] The present invention also provides a method for reducing DC bus capacitor ripple current.
[0005] To address the above problems, the present invention provides a system for reducing DC bus capacitor ripple current, the system comprising:
[0006] The DC bus capacitor C1 is connected to the positive and negative terminals of the battery, respectively, and is used to store the battery's electrical energy or discharge it to the motor.
[0007] The inverter circuit is connected to the DC bus capacitor C1 and the motor respectively, and is used to convert DC power into AC power to drive the motor.
[0008] The current sampling circuit, which is connected in series with the DC bus capacitor C1, is used to collect the magnitude and direction of the current flowing through the DC bus capacitor C1.
[0009] The energy storage inductor L1 has one end connected to the positive terminal of the battery and the other end connected to the positive terminal of the DC bus capacitor C1, and is used to store the battery's electrical energy or discharge it to the motor.
[0010] The control circuit is connected to the energy storage inductor L1 and the current sampling circuit respectively. It acquires the current data collected by the current sampling circuit and controls the energy storage inductor L1 to store the battery's electrical energy or discharge it to the motor based on the acquired data, so as to reduce the DC bus capacitor ripple current.
[0011] The control circuit includes a switch module and a control module. The control module is connected to the output terminal of the switch module and the current sampling circuit, respectively. The switch module is also connected to the energy storage inductor L1 and the negative terminal of the battery.
[0012] Furthermore, the switching module includes a switching transistor Q7, which is an NMOS transistor. Its drain is connected to one end of the energy storage inductor L1, its source is connected to the negative terminal of the battery, and its gate is connected to the output terminal of the control module.
[0013] Furthermore, the control module is a pulse width modulator, the input of which is connected to the current sampling circuit. Based on the data from the current sampling circuit, it outputs a pulse width signal to control the switching transistor Q7 to turn on or off.
[0014] The current sampling circuit includes a current sensor and a data processing module. The current sensor is connected in series with the DC bus capacitor C1, and its output terminal is connected to the input terminal of the data processing module. The output terminal of the data processing module is connected to the input terminal of the control circuit.
[0015] The inverter circuit includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6. The first switch Q1 and the second switch Q2, the third switch Q3 and the fourth switch Q4, the fifth switch Q5 and the sixth switch Q6 respectively form three sets of parallel half-bridge circuits.
[0016] Furthermore, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are all IGBTs. The collectors of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the positive terminal of the DC bus capacitor C1, and the emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the collectors of the second switch Q2, the fourth switch Q4, and the sixth switch Q6, respectively. The emitters of the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are connected to the negative terminal of the DC bus capacitor C1.
[0017] Furthermore, the motor is a three-phase AC motor, with its three phases connected to the emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5, respectively.
[0018] The present invention also provides a method for reducing DC bus capacitor ripple current, the method comprising the following steps:
[0019] a. The current sampling circuit obtains the magnitude and direction of the current flowing through the DC bus capacitor C1 and sends the collected data to the control circuit.
[0020] b. The control circuit controls the energy storage inductor L1 to store battery energy or discharge to the motor based on the received data, so as to reduce the DC bus capacitor ripple current.
[0021] Further, step b includes:
[0022] b1. When the motor is not working, the battery charges the DC bus capacitor C1. The control circuit controls the energy storage inductor L1 to store the battery's electrical energy according to the received data, so as to reduce the current of the battery charging the DC bus capacitor C1.
[0023] b2. When the motor performs work, the DC bus capacitor C1 discharges to the motor. The control circuit controls the energy storage inductor L1 to discharge to the motor according to the received data, so as to reduce the discharge current of the DC bus capacitor C1.
[0024] The contribution of this invention lies in the following: An energy storage inductor L1 is placed between the positive terminal of the battery and the positive terminal of the DC bus capacitor C1. The control circuit controls the energy storage inductor L1 to charge or discharge to the motor according to the direction and magnitude of the current flowing through the DC bus capacitor C1, thereby reducing the charging or discharging current of the DC bus capacitor C1, and consequently reducing the ripple current of the DC bus capacitor C1. This reduces the temperature rise of the DC bus capacitor during operation, thus extending its service life. This invention reduces the ripple current of the DC bus capacitor C1 through the energy storage inductor L1, eliminating the need for additional heat dissipation treatment for the capacitor itself and the use of large-volume, high-capacity DC bus capacitors. It is not only simple in structure and low in cost, but also highly reliable. [Attached Image Description]
[0025] Figure 1 This is a schematic diagram of the principle of the present invention.
[0026] Figure 2 This is the circuit schematic diagram of the present invention.
[0027] Figure 3 This is a flowchart of the method of the present invention.
[0028] Figure 4 This is the circuit diagram of the present invention when the motor is not performing work.
[0029] Figure 5 This is a circuit diagram of the motor performing work according to the present invention.
Detailed Implementation Methods
[0030] The following embodiments are further explanations and supplements to the present invention and do not constitute any limitation on the present invention.
[0031] Referring to Figure 1, the DC bus capacitor ripple current reduction system of the present invention includes a DC bus capacitor C1, an inverter circuit 30, a current sampling circuit 40, an energy storage inductor L1, and a control circuit 50. The energy storage inductor L1 is located between the positive terminal of the DC bus capacitor C1 and the positive terminal of the battery 10. The current sampling circuit 40 collects the magnitude and direction of the current flowing through the DC bus capacitor C1 and sends the collected data to the control circuit 50. The control circuit 50 controls the energy storage inductor L1 to store the electrical energy of the battery 10 or discharge it to the motor 20 according to the received data, so as to reduce the DC bus capacitor ripple current, reduce the temperature rise of the DC bus capacitor during operation, and thus extend the service life of the DC bus capacitor C1.
[0032] Specifically, such as Figure 1 , Figure 2 As shown, one end of the DC bus capacitor C1 is connected to the positive terminal of the battery 10 and the input terminal of the inverter circuit 30, and the other end is connected to the negative terminal of the battery 10 and the output terminal of the inverter circuit 30. The DC bus capacitor C1 is used to store electrical energy from the battery 10 or to discharge energy to the motor 20. Specifically, when the motor 20 is not operating, the electrical energy from the battery 10 is stored in the DC bus capacitor C1; when the motor 20 is operating, the DC bus capacitor C1 outputs the stored electrical energy to the motor to drive it.
[0033] like Figure 1 , Figure 2 As shown, motor 20 is a three-phase AC motor, which is connected to DC bus capacitor C1 via inverter circuit 30. Inverter circuit 30 is connected to both DC bus capacitor C1 and motor 20, converting DC power to AC power to drive motor 20. Inverter circuit 30 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6. The first switch Q1 and the second switch Q2, the third switch Q3 and the fourth switch Q4, and the fifth switch Q5 and the sixth switch Q6 form three sets of parallel half-bridge circuits to drive motor 20. Specifically, as shown... Figure 2In the illustrated embodiment, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are all IGBTs. The collectors of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the positive terminal of the DC bus capacitor C1, and the emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the collectors of the second switch Q2, the fourth switch Q4, and the sixth switch Q6, respectively. The emitters of the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are connected to the negative terminal of the DC bus capacitor C1, respectively. The three phases of the motor 20 are connected to the emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5, respectively. Of course, the first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are not limited to IGBTs; other switching devices can also be used, and no limitation is made here.
[0034] like Figure 1 , Figure 2 As shown, a current sampling circuit 40 is connected in series with the DC bus capacitor C1. The output of the current sampling circuit 40 is connected to the control circuit 50. It is used to collect the magnitude and direction of the current flowing through the DC bus capacitor C1 and send the collected data to the control circuit 50. The current sampling circuit 40 includes a current sensor Ic and a data processing module 41. The current sensor Ic is connected in series with the DC bus capacitor C1, and its output is connected to the input of the data processing module 41. The output of the data processing module 41 is connected to the input of the control circuit 50. When the motor 20 is not working, the DC bus capacitor C1 stores the electrical energy of the battery 10. At this time, the current flows from the positive terminal of the battery 10 to the DC bus capacitor C1, and the data processing module 41 collects the magnitude and direction of this current through the current sensor Ic. When the motor 20 is working, the DC bus capacitor C1 discharges to the motor 20. At this time, the current flows from the positive terminal of the DC bus capacitor C1 to the motor 20, and the data processing module 41 collects the magnitude and direction of this current through the current sensor Ic. The data processing module 41 processes the collected data and sends the processed data to the control circuit 50.
[0035] like Figure 1 , Figure 2 As shown, one end of the energy storage inductor L1 is connected to the positive terminal of the battery 10, and the other end is connected to the positive terminal of the DC bus capacitor C1, used to store the electrical energy of the battery 10 or discharge it to the motor 20. The energy storage inductor L1 is controlled by the control circuit 50 to store the electrical energy of the battery 10 or discharge it to the motor 20. When the motor 20 is not working, the control circuit 50 controls the energy storage inductor L1 to store the electrical energy of the battery 10, thereby reducing the charging current of the DC bus capacitor C1; when the motor 20 is working, the control circuit 50 controls the energy storage inductor L1 to discharge it to the motor 20, thereby reducing the discharging current of the DC bus capacitor C1.
[0036] Specifically, such as Figure 1 , Figure 2 As shown, the control circuit 50 includes a switch module 51 and a control module 52. The control module 52 is connected to both the switch module 51 and the output terminal of the current sampling circuit 30. The switch module 51 is also connected to both the energy storage inductor L1 and the negative terminal of the battery 10. Figure 2 In the illustrated embodiment, the switching module 51 includes a switching transistor Q7, which is an NMOS transistor. Its drain is connected to one end of the energy storage inductor L1, its source is connected to the negative terminal of the battery 10, and its gate is connected to the output terminal of the control module 52. The control module 52 is a pulse width modulator (PWM), and its input terminal is connected to the current sampling circuit 30. The control module 52 outputs a pulse width signal based on the current magnitude and direction data sent by the current sampling circuit 30, controlling the switching transistor Q7 to turn on or off, thereby controlling the charging or discharging of the energy storage inductor L1. When the current sampled by the current sampling circuit 30 is a charging current, the control module 52 controls the pulse width of the switching transistor Q7, causing the energy storage inductor L1 to store energy from the battery 10. This reduces the charging current supplied by the battery 10 to the DC bus capacitor C1, indirectly suppressing the ripple current during the charging process of the DC bus capacitor C1. When the current sampled by the current sampling circuit 30 is the discharge current, the control module 52 controls the pulse width of the switching transistor Q7, so that the energy storage inductor L1 outputs energy to the motor 20, thereby reducing the discharge current of the DC bus capacitor C1 and indirectly suppressing the magnitude of the ripple current during the discharge of the DC bus capacitor C1.
[0037] like Figure 3 As shown, the method for reducing DC bus capacitor ripple current in this embodiment includes the following steps:
[0038] S10, the current sampling circuit 30 acquires the magnitude and direction of the current flowing through the DC bus capacitor C1, and sends the acquired data to the control circuit 50.
[0039] In this step, the current sampling circuit 30 obtains the magnitude and direction of the current of the DC bus capacitor C1 through the current sensor Ic, and sends the collected data to the control circuit 50.
[0040] S20, the control circuit 50 controls the energy storage inductor L1 to store the electrical energy of the battery 10 or to discharge the energy to the motor 20 according to the received data, so as to reduce the ripple current of the DC bus capacitor C1.
[0041] In this step, the motor 20 in this embodiment is a three-phase AC motor, which is connected to the DC bus capacitor C1 through the inverter circuit 30. The inverter circuit 30 includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6. The first switch Q1 and the second switch Q2, the third switch Q3 and the fourth switch Q4, the fifth switch Q5 and the sixth switch Q6 respectively form three sets of parallel half-bridge circuits to drive the motor 20 to run.
[0042] like Figure 2 As shown, the control circuit 50 includes a switching transistor Q7 and a control module 52. The control module 52 analyzes and processes the current data collected by the current sampling circuit 30. When the motor 20 is not performing work, the current collected by the current sampling circuit 30 is the charging current. The control module 52 then controls the pulse width of the switching transistor Q7, causing the energy storage inductor L1 to store energy from the battery 10, thereby reducing the charging current supplied by the battery 10 to the DC bus capacitor C1 and indirectly suppressing the ripple current during the charging process of the DC bus capacitor C1. When the motor 20 is performing work, the current collected by the current sampling circuit 30 is the discharging current. The control module 52 then controls the pulse width of the switching transistor Q7, causing the energy storage inductor L1 to output energy to the motor 20, thereby reducing the discharging current of the DC bus capacitor C1 and indirectly suppressing the ripple current during the discharging process of the DC bus capacitor C1.
[0043] Specifically, such as Figure 4 In the illustrated embodiment, when the first switch Q1, the third switch Q3, and the fifth switch Q5 of the inverter circuit 40 are off, and the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are on, the three-phase windings of the motor 20 are short-circuited and do no work. The DC bus capacitor C1 does not provide energy output, so the bus current Id is equal to 0. At this time, the battery 10 charges the DC bus capacitor C1. The control module 52 controls the pulse width of the switching transistor Q7, causing the energy storage inductor L1 to store energy from the battery 10, thereby reducing the charging current supplied by the battery 10 to the DC bus capacitor C1 and indirectly suppressing the ripple current during the charging process of the DC bus capacitor C1.
[0044] like Figure 5In the illustrated embodiment, when the first switch Q1 of the inverter circuit 40 is turned on, the third switch Q3 and the fifth switch Q5 are turned off, the second switch Q2 is turned off, and the fourth switch Q4 and the sixth switch Q6 are turned on, current flows through the three-phase windings of the motor 20, performing work. The DC bus capacitor C1 provides energy output, and the bus current Id is not 0. At this time, the DC bus capacitor C1 discharges, providing energy output to the motor 20. The control module 52 controls the pulse width of the switch transistor Q7 through the current data collected by the current sampling circuit 30, so that the energy storage inductor L1 outputs energy to the motor 20, thereby reducing the magnitude of the discharge current of the DC bus capacitor C1 and indirectly suppressing the magnitude of the ripple current during the discharge of the DC bus capacitor C1.
[0045] Therefore, the method for reducing the ripple current of the DC bus capacitor in this embodiment uses the control circuit 50 to control the energy storage inductor L1 to store electrical energy or discharge it to the motor according to the direction and magnitude of the current flowing through the DC bus capacitor C1. This reduces the charging or discharging current of the DC bus capacitor C1, thereby reducing the ripple current of the DC bus capacitor C1 and decreasing the temperature rise of the DC bus capacitor during operation, thus extending the service life of the DC bus capacitor C1. This invention reduces the ripple current of the DC bus capacitor C1 through the energy storage inductor L1, eliminating the need for additional heat dissipation treatment for the capacitor itself and the use of large-volume, high-capacity DC bus capacitors. It is simple in structure, low in cost, and highly reliable.
[0046] Although the present invention has been disclosed through the above embodiments, the scope of protection of the present invention is not limited thereto. Any modifications or substitutions made to the above components without departing from the concept of the present invention shall fall within the scope of the claims of the present invention.
Claims
1. A system for reducing direct current bus capacitor ripple current, the system comprising: The system includes: The DC bus capacitor C1 has its negative terminal connected to the negative terminal of the battery, and is used to store the battery's electrical energy or discharge it to the motor. The inverter circuit is connected to the DC bus capacitor C1 and the motor respectively, and is used to convert DC power into AC power to drive the motor. The current sampling circuit is used to collect the magnitude and direction of the current flowing through the DC bus capacitor C1; The energy storage inductor L1 has one end connected to the positive terminal of the battery and the other end connected to the positive terminal of the DC bus capacitor C1, and is used to store the battery's electrical energy or discharge it to the motor. The control circuit includes a switching module and a control module. The control module is connected to both the switching module and the output of the current sampling circuit. The switching module is also connected to the other end of the energy storage inductor L1 and the negative terminal of the battery. The control circuit acquires the current data collected by the current sampling circuit and controls the energy storage inductor L1 to store battery energy or discharge to the motor based on the acquired data, thereby reducing the DC bus capacitor ripple current. The specific steps include: a. The current sampling circuit obtains the magnitude and direction of the current flowing through the DC bus capacitor C1 and sends the collected data to the control circuit. b. The control circuit controls the energy storage inductor L1 to store the battery's electrical energy or discharge it to the motor based on the received data, so as to reduce the DC bus capacitor ripple current. Step b includes: b1. When the motor is not working, the battery charges the DC bus capacitor C1. The control circuit controls the energy storage inductor L1 to store the battery's electrical energy according to the received data, so as to reduce the current of the battery charging the DC bus capacitor C1. b2. When the motor performs work, the DC bus capacitor C1 discharges to the motor. The control circuit controls the energy storage inductor L1 to discharge to the motor according to the received data, so as to reduce the discharge current of the DC bus capacitor C1.
2. The system for reducing DC bus capacitor ripple current as described in claim 1, characterized in that, The switching module includes a switching transistor Q7, which is an NMOS transistor. Its drain is connected to one end of the energy storage inductor L1, its source is connected to the negative terminal of the battery, and its gate is connected to the output terminal of the control module.
3. The system for reducing DC bus capacitor ripple current as described in claim 2, characterized in that, The control module is a pulse width modulator. The input terminal of the pulse width modulator is connected to the current sampling circuit. It outputs a pulse width signal based on the data from the current sampling circuit to control the switching transistor Q7 to turn on or off.
4. The system for reducing DC bus capacitor ripple current as described in claim 1, characterized in that, The current sampling circuit includes a current sensor and a data processing module. The current sensor is connected in series with the DC bus capacitor C1, and its output terminal is connected to the input terminal of the data processing module. The output terminal of the data processing module is connected to the input terminal of the control circuit.
5. The system for reducing DC bus capacitor ripple current as described in claim 1, characterized in that, The inverter circuit includes a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6. The first switch Q1 and the second switch Q2, the third switch Q3 and the fourth switch Q4, the fifth switch Q5 and the sixth switch Q6 respectively form three sets of parallel half-bridge circuits.
6. The system for reducing DC bus capacitor ripple current as described in claim 5, characterized in that, The first switch Q1, the second switch Q2, the third switch Q3, the fourth switch Q4, the fifth switch Q5, and the sixth switch Q6 are all IGBTs. The collectors of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the positive terminal of the DC bus capacitor C1. The emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5 are connected to the collectors of the second switch Q2, the fourth switch Q4, and the sixth switch Q6. The emitters of the second switch Q2, the fourth switch Q4, and the sixth switch Q6 are connected to the negative terminal of the DC bus capacitor C1.
7. The system for reducing DC bus capacitor ripple current as described in claim 6, characterized in that, The motor is a three-phase AC motor, and its three phases are respectively connected to the emitters of the first switch Q1, the third switch Q3, and the fifth switch Q5.