Drive Motor DC-DC Converter Topology
By adopting a DC-DC converter topology composed of a zero-voltage switching boost and buck converter and an improved motor inverter in electric vehicles, the problem of inefficiency of driving motor converters under high duty cycles in the prior art is solved, and efficient and low-cost energy conversion and control performance improvements are achieved.
Patent Information
- Application Number
- CN202411953191.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2025-04-04
AI Technical Summary
In existing electric vehicles, when the DC-DC converter driving the motor operates at a high duty cycle, the semiconductor device suffers significant conduction losses, resulting in additional losses and electrical noise, limiting the switching frequency, and being inefficient at low speeds.
The drive motor DC-DC converter topology is constructed using a zero-voltage switch boost buck converter and an improved motor inverter, which maximizes efficiency by connecting the zero-voltage switch boost buck converter into each phase of the motor inverter and activate or deactivate each converter according to the power level.
It realizes high-efficiency conversion with low cost at high, medium and low power, can transmit energy in two directions, provide electrical isolation, reduce component count, is easy to control and implement, and reduces electrical noise, and improves the control performance of permanent magnet synchronous motors in electric vehicles.
Smart Images
Figure CN119765865A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of electric vehicles, and in particular to a topological structure of a DC-DC converter for a driving motor. Background Art
[0002] In recent years, the boom in electric propulsion in the field of electric vehicles has promoted the use of power converters in vehicles. In today's electric or hybrid vehicle architecture, there may be three voltage levels: the high-voltage battery, which is charged by the grid, regenerative braking system or internal combustion engine, powers the traction system and the 12V low-voltage system used by most vehicle electronic systems. In some cars, there is also a 48V voltage level responsible for systems such as start-stop system, regenerative braking energy storage, suspension height adjustment, etc. Due to the large number of DC voltage levels that may exist in the same car, and in order to eliminate additional batteries, DC-DC converters become indispensable.
[0003] Permanent magnet synchronous motors (PMSMs) have high efficiency, high torque density, and low torque ripple, making them ideal for high-performance electric vehicles; e.g. Fig.13 As shown in the figure, it is a traditional permanent magnet synchronous motor power system with a boost converter. In the DC-DC topology, the most commonly used is the boost converter operating in continuous conduction mode (CCM). The boost converter is favored and adopted because it is a well-known topology and its simplicity is particularly prominent. When the converter must operate at a high duty cycle, that is, to reduce the battery voltage (v bat ) and increase the output voltage (v b ), semiconductor devices start to suffer significant conduction losses. In addition, the switching devices operate in hard-switching mode, which translates into high voltage and current peaks, resulting in additional losses, which limits the switching frequency and generates electrical noise. As a result, the cooling system and differential and common-mode filters require greater size and weight. The inductor L that ensures CCM and withstands the motor current B It also results in a larger component. In addition, the bus voltage must be proportional to the EMF, which in turn is proportional to the mechanical rotational speed of the motor. Therefore, a low bus voltage must be used at low speeds, and as the rotational speed increases, the bus voltage increases proportionally. This means that in some cases, the DC-DC converter must increase v b Instead of boosting the voltage, the DC bus voltage is stepped down to a value below the battery voltage. Although increasing the DC bus voltage can bring advantages, it is inefficient at low speeds, low torques, and / or low power usage. Therefore, a drive motor DC-DC converter topology is needed to address the above issues. Summary of the invention
[0004] The object of the present invention is to provide a topological structure of a DC-DC converter for driving a motor, so as to solve the problems existing in the prior art mentioned in the above background technology.
[0005] To achieve the above object, the present invention provides the following technical solutions:
[0006] The drive motor DC-DC converter topology includes a zero-voltage switching boost-buck converter and a motor inverter. The phase line of the motor inverter is connected to a zero-voltage switching boost-buck converter for increasing and decreasing the bus voltage. The zero-voltage switching boost-buck converter can be switched to an optimal working state according to the working conditions.
[0007] Preferably, the motor inverter comprises two switches Q S1 , Q S2 And bus capacitance C b The output end of the motor inverter is connected to the input end of the permanent magnet synchronous motor.
[0008] Preferably, the zero voltage switching step-up / step-down converter comprises four switches Q P1 , Q P2 , Q P3 , Q P4 , inductor L and transformer, including DC blocking capacitor C to avoid transformer saturation DC,P A capacitor C is connected between the positive and negative electrodes of the input terminal of the zero voltage switching step-up / step-down converter. i The secondary side of the transformer is connected in series with a capacitor C DC,S .
[0009] Preferably, each phase of the three phases A, B, and C of the motor inverter is connected to a zero voltage switching step-up and step-down converter.
[0010] The present invention also provides a control method for a topological structure of a DC-DC converter for a driving motor, which specifically comprises the following steps:
[0011] The topology structure allows operation at two optimal points in a full-bridge implementation, the first optimal point is 2N, but one of the two full-bridge branches keeps the lower switch permanently turned on and the upper switch permanently turned off, that is, the topology structure becomes a half-bridge implementation, whose optimal operating point is N, achieving switching between the two optimal points 2N and N.
[0012] Compared with the prior art, the present invention has the following beneficial effects:
[0013] The present invention adopts a zero-voltage switching boost-buck converter and an improved motor inverter to form a DC-DC converter topology structure for driving a motor, and connects the zero-voltage switching boost-buck converter to each phase of the three phases A, B, and C of the motor inverter, and activates or deactivates each zero-voltage switching boost-buck converter according to the power level to maximize efficiency, thereby achieving low cost at high, medium, and low power, and being able to transmit energy in two directions, and also providing electrical isolation, reducing the number of components, being easy to control and implement, reducing electrical noise, and improving the control performance of the permanent magnet synchronous motor in the electric vehicle. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 Electrical schematic using a full bridge configuration for the inventive topology.
[0015] Figure 2 Electrical schematic using a half-bridge configuration for the inventive topology.
[0016] Figure 3 Electrical schematic for the topology of the present invention using a full-bridge implementation and operating under half-bridge conditions.
[0017] Figure 4 It is a waveform diagram of the topological structure of the present invention.
[0018] Figure 5 The topological structure of the present invention is a Electrical schematic diagram of state one when greater than zero.
[0019] Figure 6 The topological structure of the present invention is a Electrical schematic diagram of state two when greater than zero.
[0020] Figure 7 The topological structure of the present invention is a Electrical schematic diagram of state three when greater than zero.
[0021] Figure 8 The topological structure of the present invention is a Electrical schematic diagram of state four when greater than zero.
[0022] Fig. 9 The topological structure of the present invention is a Electrical schematic diagram of state one when less than zero.
[0023] Fig.10 The topological structure of the present invention is a Electrical schematic diagram of state two when the voltage is less than zero.
[0024] Fig.11 The topological structure of the present invention is a Electrical schematic diagram of state three when the voltage is less than zero.
[0025] Fig.12 The topological structure of the present invention is a Electrical schematic diagram of state four when the voltage is less than zero.
[0026] Fig.13 The electrical schematic of a conventional powertrain with a boost converter. DETAILED DESCRIPTION
[0027] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.
[0028] See also Figure 1-13 , the present invention provides the following technical solutions:
[0029] A drive motor DC-DC converter topology structure includes a zero voltage switching boost-buck converter and a motor inverter, wherein the phase line of the motor inverter is connected with a zero voltage switching boost-buck converter for increasing and decreasing the bus voltage, and the zero voltage switching boost-buck converter can be switched to an optimal working state according to the working conditions; each phase of the three phases A, B, and C of the motor inverter is connected with a zero voltage switching boost-buck converter; the scheme also allows each zero voltage switching boost-buck converter to be activated or deactivated according to the power level to maximize efficiency.
[0030] The motor inverter comprises two switches Q S1 , Q S2 And bus capacitance C b , bus capacitance C b The three phases are shared, so the voltage ripple is reduced nearly three times, and the output end of the motor inverter is connected to the input end of the permanent magnet synchronous motor.
[0031] The zero voltage switching boost-buck converter includes four switches Q P1 , Q P2 , Q P3 , Q P4 , inductor L and transformer. Inductor L is used to limit and regulate current. The transformer not only provides electrical isolation but also provides nominal voltage gain N. It also includes DC blocking capacitor C to avoid transformer saturation. DC,P A capacitor C is connected between the positive and negative electrodes of the input terminal of the zero voltage switching step-up / step-down converter. i The secondary side of the transformer is connected in series with a capacitor C DC,S .
[0032] The present invention also provides a control method for a topological structure of a DC-DC converter for a driving motor, which specifically comprises the following steps:
[0033] like Figure 1As shown, this implementation allows operation within a wider input and output voltage range around the optimal point. The topology allows operation at two optimal points in a full-bridge implementation, the first optimal point being 2N, but one of the two full-bridge branches keeps the lower switch permanently turned on and the upper switch permanently turned off, that is, the topology becomes a half-bridge implementation with an optimal operating point of N, achieving switching between the two optimal points 2N and N.
[0034] Figure 1 The topology can be transformed into Figure 2 The topology is able to switch between two optimal points: 2N and N. This avoids the main disadvantage of zero-voltage switching boost-buck converters when the boost requirement is high, that is, the efficiency will be greatly reduced; the rms current of the semiconductors in the motor inverter stage is slightly smaller, about 10% lower, because part of the power is directly transferred from the primary side transistor to the motor; another major advantage of this scheme over the traditional boost converter is the realization of zero voltage switching on the boost and buck sides, which reduces switching losses and electromagnetic noise.
[0035] In order to facilitate the understanding of the operation process of the topology structure, the following only describes the components Figure 1 The analysis is performed on one of the three phases (phase A) of the combined converter in Figure 1. This analysis is equivalent to each of the three phases that make up the converter. Based on the state of the switch and the direction of the current flowing to the motor, the operation of the converter can be divided into eight states. a When it is greater than zero, there are four states, corresponding to Figure 5-8 , when i a When it is less than zero, there are four states, corresponding to Figure 9-12 .
[0036] In a switching cycle T sw Internally, the inductor current i L , primary side voltage v p and the secondary side voltage v s The waveform, and when i a The four states of positive Figure 4 As explained in the figure, the duty cycle of the primary side voltage is named d1, and the duty cycle of the secondary side voltage is denoted as d2, v p and v s The phase shift between
[0037] In the first state, if Figure 5 As shown, Q P1 and Q P4 is activated, and Q P2 and Q P3 This generates a positive voltage at the first terminal of the inductor L, namely +v bat , v pOn the other hand, on the secondary side, i.e. the inverter side, the lower transistor Q S2 is activated, generating a negative voltage -v on the secondary side b / 2. This high voltage difference across the inductor causes the current flowing through it to increase rapidly. At the beginning of the switching cycle, i L is negative, so the diode will start to conduct until the channel of the MOSFET is fully turned on, or in the case of an IGBT, i L Reverse polarity. In this state, part of the power is transferred directly from the primary side to the motor windings.
[0038] In the second state, if Figure 6 As shown, Q S2 Shutdown and Q S1 The switch is turned on, and the secondary V s A positive voltage +v is generated on the side b / 2. In this state, the voltage difference across the inductor L is relatively small, so the current hardly changes. S1 is activated, current flows into and out of the bus capacitor C b .
[0039] In the third state, if Figure 7 As shown, Q P1 and Q P4 Off, while Q P2 and Q P3 When this happens, the voltage on the primary side reverses to -v bat , resulting in L Rapidly decreases. Similar to the first state, once the transistor Q P1 turns off, current starts flowing through transistor Q P2 and Q P3 The anti-parallel diodes of the transistors are then turned on.
[0040] In the fourth state, if Figure 8 As shown, where v s Reverse to -vb / 2. Since the voltage difference across the inductor L is small, i L The slope is very low.
[0041] in i a >0 during these states, the bus capacitance C b is discharging. Otherwise, when i a When it becomes negative, C b Charging. Figure 9-12 As explained in the diagram, it can be seen that the phase current now flows into C bTherefore, the proposed drive motor DC-DC converter topology has high efficiency and high power density at the maximum inverter power, low cost at high, medium and low power, and can transfer energy in two directions, and also provides electrical isolation, reduced component count, easy control and implementation, and reduced electrical noise.
[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. Drive motor DC-DC converter topology, characterized in that: It includes a zero voltage switching boost-buck converter and a motor inverter. The phase line of the motor inverter is connected to a zero voltage switching boost-buck converter for increasing and decreasing the bus voltage. The zero voltage switching boost-buck converter can be switched to an optimal working state according to working conditions.
2. The topological structure of the DC-DC converter for driving the motor according to claim 1, characterized in that: The motor inverter includes two switches Q S1 , Q S2 And bus capacitance C b The output end of the motor inverter is connected to the input end of the permanent magnet synchronous motor.
3. The topological structure of the DC-DC converter for driving the motor according to claim 1, characterized in that: The zero voltage switching boost-buck converter includes four switches Q P1 , Q P2 , Q P3 , Q P4 , inductor L and transformer, including DC blocking capacitor C to avoid transformer saturation DC,P A capacitor C is connected between the positive and negative electrodes of the input terminal of the zero voltage switching step-up / step-down converter. i The secondary side of the transformer is connected in series with a capacitor C DC,S .
4. The topological structure of the DC-DC converter for driving the motor according to claim 1, characterized in that: Each phase of the three phases A, B and C of the motor inverter is connected to a zero voltage switching step-up and step-down converter.
5. A control method for a DC-DC converter topology structure of a drive motor as claimed in any one of claims 1 to 4, characterized in that: The specific steps include: The topology structure allows operation at two optimal points in a full-bridge implementation, the first optimal point is 2N, but one of the two full-bridge branches keeps the lower switch permanently turned on and the upper switch permanently turned off, that is, the topology structure becomes a half-bridge implementation, whose optimal operating point is N, achieving switching between the two optimal points 2N and N.