Claims:1. A hybrid electric vehicle using bi-directional DC-DC conversion apparatus, the hybrid electric vehicle comprising:
a permanent magnet brushless DC (PMBLDC) motor (201) which is controlled by using three-phase inverters;
a bi-directional DC-DC converter (107) fed the PMBLDC motor in a motoring mode where the bi-directional DC-DC converter (107) plays a vital role in two modes of operation; and
a PIC microcontroller (110) which controls the movements of pneumatic valves (102) and controls signals for the bi-directional DC-DC converter (107);
wherein the two modes of operation consisting of an engine mode and a motoring or generating mode such that in the engine mode, the vehicle movement is carried out by the engine alone (103), and in the motoring or generating mode, the vehicle movement is carried out by the motor (105) which is powered by a battery (111).
2. The hybrid electric vehicle as claimed in claim 1, wherein the motor (105) and the engine (103) are coupled together with a gearbox (104).
3. The hybrid electric vehicle as claimed in claim 1, wherein the motor (105) can operate in 4th quadrant delivering power to store in the lead-acid battery (111) through the three-phase inverter.
4. The hybrid electric vehicle as claimed in claim 1, wherein the PMBLDC motor (201) is selected for attaining high- speed constant-power operation which is particularly essential for electric vehicles.
5. The hybrid electric vehicle as claimed in claim 1, wherein the bi-directional DC-DC converter (107) is necessary for the hybrid electric vehicle topologies in which the voltage of the battery (111) and the DC-link are not equal.
6. The hybrid electric vehicle as claimed in claim 4, wherein the bi-directional DC-DC converter (107) works on both directions of electric power flow.
7. The hybrid electric vehicle as claimed in claim 4, wherein an input voltage of the bi-directional DC-DC converter (107) is about 12V and it boosts the voltage to 24V.
, Description:[0030] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0031] In the following description, numerous specific details are outlined to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.
[0032] FIG. 1 illustrates a block diagram of hybrid electric vehicle using a bi-directional DC-DC conversion apparatus, in accordance with an embodiment of the present invention. In the proposed system aims to design user convenient Hybrid Electric Vehicle which can operate in 2 modes based on the traffic density. As shown in fig.1, the mode selection is done through a PIC Microcontroller 110 which controls the movements of pneumatic valves 102 and control signals for the bi-directional DC-DC converters 107 as shown in Fig 1. In engine mode, the vehicle movement is carried out by engine alone 103. Since motor 105 and engine 103 are coupled together with gearbox 104, the motor can operate in 4th quadrant delivering power to store in lead-acid battery 111 through a three-phase inverter106. In the battery mode, the vehicle movement is carried out by the motor 105 which is powered by the battery 111. This can reduce the emission of flue gas.
[0033] FIG. 2 illustrates a circuit diagram of the present invention; BLDC motor shown in Fig 2 uses dc power supply 202 and its switching sequence is determined by rotor position. BLDC motor 201 phase current has rectangular waveforms and is synchronized by power devices with the back-EMF to produce constant torque in constant speed. BLDC motors are controlled using three-phase inverters and the torque in the BLDC motors 201 is similar to that of the separate excitation DC motors.
[0034] FIG. 3 illustrates the two different modes of the present invention; wherein the conventional bi-directional DC-DC converter circuit structure is illustrated in Fig.3. Depending on the placement of the auxiliary energy storage system, the bi-directional DC-DC converter can be categorized into a buck and boost type. When the energy storage system is placed on high voltage side it comes under buck type, and when placed on the low voltage side it comes under boost type.
[0035] FIG. 4 illustrates the two different time intervals of the present invention; wherein the switch should carry the current on both directions to realize the double-sided power flow. The power MOSFET (Metal-Oxide Semiconductor-Field-Effect-Transistor) or IGBT (Insulated Gate Bipolar Transistor) in parallel with a diode are the most common power switches used here because of unavailability of double-sided current flow switches.
[0036] The Bi-directional DC-DC converter plays a vital role in the two modes of operation which are discussed as follows:
[0037] Motoring mode: In this operation, the power is transferred from V battery to VDClink; Time interval 1(t0-t1): At time t0, the lower switch Q2 is turned ON and the upper switch Q1 is turned OFF with diode D1, D2 reverse biased as shown in Fig 2.4.a. During this time interval the converter operates in boost mode and the inductor is charged and current through the inductor increases. Time interval 2(t1-t2): During this interval, both switches Q1 and Q2 is turned OFF. The body diode D1 of upper switch Q1 starts conducting as shown in Fig 2.4.b. The converter output voltage is applied across the motor. As this converter operates in boost mode is capable of increasing the battery voltage to run the motor in the forward direction.
VDClink=1/(1-D) VBATTERY (1)
Where, D is the duty ratio of Q2.
[0038] Generating mode: In this mode, the power is transferred from V-load to V-battery; Time interval 3(t2-t3): At time t3, the upper switch Q1 is turned ON and the lower switch Q2 is turned OFF with diode D1, D2 reverse biased as shown in Fig 2.4.c. During this time interval, the converter operates in buck mode. Time interval 4(t3-t4): During this interval, both switches Q1 and Q2 turned OFF. The body diode D2 of lower switch Q2 starts conducting as shown in Fig 2.4.d.
V0=D1 V battery (2)
Where, D1 is the duty ratio of Q1.

[0039] FIG. 5 illustrates the motoring mode in the present invention; wherein figure depicts the bidirectional DC-DC converter fed PMBLDC motor in motoring mode. The input voltage applied to the bidirectional DC-DC converter is 12V DC from the battery. The output voltage of the bidirectional DC-DC converter is applied to the three-phase inverter whose output voltage is applied to the PMBLDC motor. The electromotive force is sensed by the hall sensor and hence it converts to gate pulse to apply for the three-phase inverter. The input voltage given to the bidirectional DC-DC converter is about 12V and it boosts the voltage to 24V. The actual voltage obtained is compared with the reference voltage and the output is given to the PID controller.
[0040] FIG. 6 illustrates the boost mode in the present invention; Wherein the Figure depicts the bidirectional DC-DC converter fed PMBLDC motor in generating mode. In this mode, the PMBLDC motor acts as a generator and supplies energy to the battery via the converter. The bidirectional DC-DC converter now acts as a buck converter and the current flow is from the PMBLDC motor to the battery. The battery is now charging. The input voltage to the converter is 24V and is stepped down to 12V in this buck mode of operation.
[0041] FIG. 7 illustrates the hardware implementation of the present invention; wherein the figure shows the complete hardware setup of the bidirectional DC-DC converter and PMBLDC motor in Hybrid Electric Vehicle. The circuit consists of the battery, bidirectional DC-DC converter, three-phase inverter, PMBLDC motor and microcontroller. The components are connected in accordance to circuit diagram presented. The mechanical components such as the petrol engine and accelerator along with the electrical circuits are assembled.
[0042] One or more of the components, steps, and/or functions illustrated in the Figures may be rearranged and/or combined into a single component, step, or function or embodied in several components, steps, or functions. Additional elements, components, steps, and/or functions may also be added without departing from the invention. The novel algorithms described herein may be efficiently implemented in software and/or embedded hardware.
[0043] In the description of the present specification, a reference to the term "one embodiment," "in embodiments", "an example", "an instance", or "some examples" and the description is meant in connection with the embodiment or example described the particular feature, structure, material, or characteristic included in the present invention, at least one embodiment or example. In the present specification, the term of the above schematic representation is not necessarily for the same embodiment or example. Furthermore, the particular features structures, materials, or characteristics described in any one or more embodiments or examples properly. Moreover, those skilled in the art can be described in the specification of different embodiments or examples are joined and combinations thereof.
[0044] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
[0045] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person.