Claims:We claim:
1.An integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in electric vehicles, the system comprises:
•an integrated power source consisting of a plurality of power sources connected in parallel for handling higher power range input sources;

• an integrated power electronic module consisting of a plurality of power electronic modules connected in parallel; and

•an electrical load wherein the integrated power module is connected in series to each power source of the integrated power source and the integrated power electronic module is connected in series to the vehicle motor load for obtaining maximum duty cycle operation with reduced power losses and to boost power output at power electronic module level in renewable power sources installed for powering the electric vehicle.

2. Integrated power electronic system as claimed in claim 1, wherein at least three DC power sources are paralleled to at least two power converters paralleled to the electric vehicle motor load.

3.Integrated power electronic system as claimed in claim 1, wherein the power electronic topology comprises a transformer having a primary side and a secondary side, each side including a pair of power converters and the power converter on the secondary side having two current sources connected in series to an inductance.

4. Integrated power electronic system as claimed in claim 3, wherein the primary side comprises at least two power converters connected to each other via a respective MOSFET switch and capacitor, each capacitor connected in series to a power converter; at least three DC power sources; each DC power source connected in series to a resistor; DC power source-resistor pairs connected in parallel to each other; a resistor circuit (RC) arrangement including one pair of resistor and capacitor for each DC power source, connected in series to both the power converters; at least one inductance connected in parallel to DC power sources; at least two parallelly connected pairs of diodes connected in series to the inductance and the resistor circuit arrangement; two parallely connected MOSFET switch-capacitor pairs, connected in series to each primary side power converter; wherein the two power converters connected in parallel with the first MOSFET switch is switched on for energizing the primary side for discharging a first capacitor through a first switch, inductance and a first pair of parallely connected diodes and for reverse biasing a diode by keeping the transformer in magnetized state.

5. Integrated power electronic system as claimed in claim 3, wherein the secondary side comprises two parallely connected power converters connected in parallel to an AC load.

6. An integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in electric vehicles, the system comprises:

• a transformer having a primary side and a secondary side, each side including a pair of power converters and the power converter on the secondary side having two current sources connected in series to an inductance;

• an integrated power source consisting of three power sources paralleled to two power converters in turn paralleled to the electric vehicle motor load;

• an integrated power electronic module consisting of a plurality of power electronic modules connected in parallel; and
• an electrical load;

wherein the integrated power module is connected in series to each power source of the integrated power source and the integrated power electronic module is connected in series to the vehicle motor load for providing maximum duty cycle operation with reduced power losses and for boosting the power output at the power electronic module level.

7. Integrated power electronic system as claimed in anyone of claims 1 to 6, wherein the electric vehicle is a renewable energy based electric vehicle.

8. Integrated power electronic system as claimed in anyone of claims 1 to 6, wherein the electric vehicle is a renewable energy based hybrid electric vehicle.

9. An integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in renewable energy based electric vehicles, the system comprises an integrated power conversion system with improved power electronic topology, wherein current sources are provided along with a series inductance for the connected power converters on the secondary side to continuously conduct current in the secondary side of the transformer circuit for enhancing power transfer to the connected electric vehicle load by maximizing duty cycle and by minimizing resonance oscillations occurring between the inductance of the transformer and the capacitor, during the transit period between S1 Ton (turn-on period) and Toff (Turn off period), even when the value of the reflected voltage across the primary side of the transformer is zero.

10. A method for reducing the resonance oscillations in power converters used in an electric vehicle by using the integrated power electronic system as claimed in anyone of the claims 1 to 6, wherein the method comprises the steps of:

(i) switching on the first MOSFET switch of the primary side of the transformer to apply the source voltage across the first primary side transformer too energize the transformer;

(ii) discharging a first capacitor through a first switch, inductance and a first pair of parallely connected diodes and reverse biasing the diode by keeping the transformer magnetized;

(iii) switching on the second MOSFET switch for applying voltage across the second power converter to discharge the capacitor through second switch, inductance and the first pair of diodes;

(iv) switching off the first MOSFET switch for charging the first capacitor to increase voltage of the first power converter;

(v) switching off the second MOSFET switch for charging the second capacitor for increasing the voltage of the second power converter by conducting current through second switch, inductance and the first pair of primary side diodes;

(vi) switching on the second switch of the first power converter for conducting current through a first secondary side diode, when the voltage is positive;

(vii) reflecting current to the secondary of the transformer and conducting current by the secondary side diodes;

(viii) switching on the first switch of the first power converter for conducting current through the first diode of the secondary side of the transformer, when the voltage is positive;

(ix) switching on the second switch of the first power converter for conducting current through the second diode of the secondary side of the transformer, when the voltage is negative

(x) switching on the first switch of the second power converter for conducting current through the third diode of the secondary side of the transformer, when the voltage is positive;

(xi) switching on the second switch of the second power converter for conducting current through the fourth diode of the secondary side of the transformer, when the voltage is negative;

(xii) enhancing the power transfer to the connected electric vehicle load to maximize the duty cycle by supplying a continuous flow of secondary current on the secondary side supply and by minimizing the resonant oscillations occurring during the transit period between S1 Ton (turn-on period) and Toff (Turn off period), even in the absence of a reflected voltage across the primary side of the transformer.


Dated: this day of 30th July, 2016. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to a power electronic system for reducing the resonance oscillations in power converters. In particular, the present invention relates to a power electronic system for optimal reduction of the resonance oscillations in power converters used in electric vehicles. More particularly, the present invention relates to a method for reducing the resonance oscillations in power converters used in electric vehicles.

BACKGROUND OF THE INVENTION

Currently, renewable energy sources are replacing the traditional energy sources at an increased pace. In fact, these renewable energy sources are also being introduced in automotive sector because of environmental issues with the fossil fuels like petrol and diesel producing enormous amount of greenhouse gases. In particular, these power sources based on renewable technology are most favoured in electric vehicle applications like hybrid electric vehicles (HEVs) and electric vehicles (EVs), which are priority sectors for introduction of renewable energy sources in order to reduce usage of gasoline for sequestration of CO2 as a significant step towards vehicle electrification, e.g. in electric vehicles.

Accordingly, the on-board power sources in electric vehicle have advanced to such an extent that maximum efficiency can be achieved from these renewable power sources installed on-board for powering such electric vehicles.

DISADVANTAGES WITH THE PRIOR ART

However, these on-board power sources used for powering such electric vehicles show considerable power losses in terms of the energy efficiency obtained therefrom. Since these power losses significantly reduce the overall efficiency and reliability of electric vehicles, it is imperative to optimize the efficiency of electric vehicles fitted with on-board renewable power sources.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide an improved topology and arrangement of the power electronic modules used in on-board renewable energy sources.

Another object of the present invention is to provide a compact arrangement of the power electronic modules used in on-board renewable energy sources.

Still another object of the present invention is to provide an arrangement of the power electronic modules used in on-board renewable energy sources, which has reduced power losses.

Yet another object of the present invention is to provide an arrangement of the power electronic modules used in on-board renewable energy sources, which has higher efficiency.

A further object of the present invention is to provide an arrangement of the power electronic modules used in on-board renewable energy sources, which provides maximum duty cycle.

A still further object of the present invention is to provide an arrangement of the power electronic modules used in on-board renewable energy sources, which increases the performance and reliability of the power electronics used.

A yet further object of the present invention is to provide an arrangement of the power electronic modules used in on-board renewable energy sources, which facilitate a smooth and intelligent operation of the power converters of the on-board system, irrespective of supply and load variations.

These and other objects and advantages of the present invention will become more apparent from the following description when read with the accompanying figures of drawing, which are, however, not intended to limit the scope of the present invention in any way.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided an integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in electric vehicles, the system comprises:

• an integrated power source consisting of a plurality of power sources connected in parallel for handling higher power range input sources;

• an integrated power electronic module consisting of a plurality of power electronic modules connected in parallel; and

• an electrical load;

wherein the integrated power module is connected in series to each power source of the integrated power source and the integrated power electronic module is connected in series to the vehicle motor load for obtaining maximum duty cycle operation with reduced power losses and to boost power output at power electronic module level in renewable power sources installed for powering the electric vehicle.

Typically, at least three DC power sources are paralleled to at least two power converters paralleled to the electric vehicle motor load.

Typically, the power electronic topology comprises a transformer having a primary side and a secondary side, each side including a pair of power converters and the power converter on the secondary side having two current sources connected in series to an inductance.

Typically, the primary side comprises at least two power converters connected to each other via a respective MOSFET switch and capacitor, each capacitor connected in series to a power converter; at least three DC power sources; each DC power source connected in series to a resistor; DC power source-resistor pairs connected in parallel to each other; a resistor circuit (RC) arrangement including one pair of resistor and capacitor for each DC power source, connected in series to both the power converters; at least one inductance connected in parallel to DC power sources; at least two parallelly connected pairs of diodes connected in series to the inductance and the resistor circuit arrangement; two parallely connected MOSFET switch-capacitor pairs, connected in series to each primary side power converter; wherein the two power converters connected in parallel with the first MOSFET switch is switched on for energizing the primary side for discharging a first capacitor through a first switch, inductance and a first pair of parallely connected diodes and for reverse biasing a diode by keeping the transformer in magnetized state.

Typically, the secondary side comprises two parallely connected power converters connected in parallel to an AC load.

The invention also provides an integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in electric vehicles, the system comprises:

• a transformer having a primary side and a secondary side, each side including a pair of power converters and the power converter on the secondary side having two current sources connected in series to an inductance;

• an integrated power source consisting of three power sources paralleled to two power converters in turn paralleled to the electric vehicle motor load;

• an integrated power electronic module consisting of a plurality of power electronic modules connected in parallel; and

• an electrical load;

wherein the integrated power module is connected in series to each power source of the integrated power source and the integrated power electronic module is connected in series to the vehicle motor load for providing maximum duty cycle operation with reduced power losses and for boosting the power output at the power electronic module level.

Typically, wherein the electric vehicle is a renewable energy based electric vehicle.

Typically, wherein the electric vehicle is a renewable energy based hybrid electric vehicle.

The invention further provides an integrated power electronic system configured for reducing resonance oscillations in power converters for on-board applications in renewable energy based electric vehicles, the system comprises an integrated power conversion system with improved power electronic topology, wherein current sources are provided along with a series inductance for the connected power converters on the secondary side to continuously conduct current in the secondary side of the transformer circuit for enhancing power transfer to the connected electric vehicle load by maximizing duty cycle and by minimizing resonance oscillations occurring between the inductance of the transformer and the capacitor, during the transit period between S1 Ton (turn-on period) and Toff (Turn off period), even when the value of the reflected voltage across the primary side of the transformer is zero.

The present invention provides a method for reducing the resonance oscillations in power converters used in an electric vehicle by using an integrated power electronic system, wherein the method comprises the steps of:

(a) switching on the first MOSFET switch of the primary side of the transformer to apply the source voltage across the first primary side transformer too energize the transformer;

(b) discharging a first capacitor through a first switch, inductance and a first pair of parallely connected diodes and reverse biasing the diode by keeping the transformer magnetized;

(c) switching on the second MOSFET switch for applying voltage across the second power converter to discharge the capacitor through second switch, inductance and the first pair of diodes;

(d) switching off the first MOSFET switch for charging the first capacitor to increase voltage of the first power converter;

(e) witching off the second MOSFET switch for charging the second capacitor for increasing the voltage of the second power converter by conducting current through second switch, inductance and the first pair of primary side diodes;

(f) switching on the second switch of the first power converter for conducting current through a first secondary side diode, when the voltage is positive;

(g) reflecting current to the secondary of the transformer and conducting current by the secondary side diodes;

(h) switching on the first switch of the first power converter for conducting current through the first diode of the secondary side of the transformer, when the voltage is positive;

(i) switching on the second switch of the first power converter for conducting current through the second diode of the secondary side of the transformer, when the voltage is negative;

(j) switching on the first switch of the second power converter for conducting current through the third diode of the secondary side of the transformer, when the voltage is positive;
(k) switching on the second switch of the second power converter for conducting current through the fourth diode of the secondary side of the transformer, when the voltage is negative;

(l) enhancing the power transfer to the connected electric vehicle load to maximize the duty cycle by supplying a continuous flow of secondary current on the secondary side supply and by minimizing the resonant oscillations occurring during the transit period between S1 Ton (turn-on period) and Toff (Turn off period), even in the absence of a reflected voltage across the primary side of the transformer.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows an integrated power conversion system configured according to the present invention and with power converters connected in parallel for handling higher power range input sources.

Figure 2 shows a schematic diagram of the novel power electronic system configured according to the present invention and having a plurality of power converters connected in parallel to the power source output for providing maximum duty cycle operation with reduced power losses.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows an integrated power conversion system configured according to the present invention, with power converters connected in parallel for handling higher power range input sources. In the present case, there are three power sources PS1, PS2, PS3 (however, ‘N’ number of power sources can also be connected in parallel), which are collectively connected to three power electronic modules PE1, PE2 and PE3 connected in parallel to each other, which in turn are collectively connected to a vehicle motor load VML.

The power conversion system developed as On-board applications are particularly useful in EVs and/or HEVs, which use DC power sources such as solar cells, fuel cells etc.

The Integrated power conversion system configured in accordance with the present invention includes an innovative power electronic module, which operates at comparatively lower switching frequencies.

It is configured to achieve maximum efficiency from the installed power sources and also to facilitate the addition of power sources connected in parallel for achieving higher power levels from the renewable power sources.

Each Power source is parallelly connected with resistor circuit (RC) arrangement to balance the unequal voltages they produce. It is connected to several individual power electronic modules in parallel. This has an improved and efficient switching arrangement with maximum duty cycle. This drastically reduces the resonant oscillation cycles occurring during the transit period between S1 Ton (turn-on period) and Toff (Turn off period).

Due to this configuration, maximum amount of power is transferred to the output terminal with substantially reduced switching losses in comparison to the existing systems. Connecting the power converters in parallel is basically intended to handle higher power range input sources as demonstrated in Fig.1.

Figure 2 shows a schematic diagram of the novel power electronic system having power converters connected in parallel to the power source output for providing maximum duty cycle operation with reduced power losses.

The novelty of the proposed topology of the power electronic system is in the introduction of the current source with series inductances Lc and Ld for both the power converters disposed on the secondary side, which induces the current to flow continuously in the secondary side of the circuit in order to avoid unnecessary resonance oscillations between L of the transformer and the capacitor, for increasing the efficiency and to facilitate an efficient usage of the switching cycle. This power electronic system is configured parallely connected with the power source output, since the modules taken into consideration are designed to handle only smaller power levels individually. This developed power electronics topology provides maximum duty cycle operation with substantially reduced power losses. For more effectiveness, it can also be connected to individual solar cell or fuel cell module to boost the output power at the module level.

The schematic power electronic system in Figure 2 includes: three DC power sources Vdc1, Vdc2,Vdc3; resistor arrangement R1,R2,R3 for voltage sources; capacitor arrangement C1,C2,C3 for voltage sources; capacitances across switches Cb1, Cb2; capacitance across output Co; MOSFET Switches S1, S2, Sa, Sb, Sc, Sd; secondary side diodes D1, D2, D3, D4; transformers Tr1, Tr2 for Power converter 1 and Power Converter 2 respectively; current sources CS1,CS2 for Power converter 1 and Power Converter 2 respectively; and Inductances Lc, Ld.

Accordingly, the new power electronic schematic of Fig. 2 includes three DC power sources connected in parallel and connected to two power converters, which in turn are also connected in parallel to the load. The number of power converters can be suitably increased (Fig. 1) to handle the input power capacity.

WORKING STAGES OF POWER ELECTRONICS TOPOLOGY

STAGE 1- When switch S1 is ON, the source voltage is applied across the primary winding of transformer Tr1 and it starts to energize. The capacitor C4 discharges through switch S1, inductance La and diodes DL3 and DL4. Diodes are paralleled for accommodating higher discharge currents. Once Capacitor C4 completely discharges, diode DL3 gets reverse biased. However, the transformer continues to be magnetized. For power converter 2, when S2 is ON, voltage gets applied across Tr2 and capacitor C4 discharges through S2, La and diodes DL3, DL4.

STAGE 2- When switch S1 is OFF, current flows through two paths. One is through the capacitance Cb1, and the other is through C4 and diode DL3, DL1. This current charges Capacitor C4 and its voltage starts to increase. For power converter 2, when S2 is OFF, the current flows through Cb2 and the other is through C4 and diodes DL1, DL2.

STAGE 3- The current gets reflected to the secondary side of the transformer and the secondary diodes (out of D1, D2, D3, D4) begins to conduct. If this voltage is positive, then Sa is ON and current flows through D1. If this voltage is negative, then Sb is ON and current flows through D2 for power converter 1. For power converter 2 in parallel, when voltage is positive, Sc is ON, current flows through D3. When voltage is negative, Sd is ON, current flows through D4.

STAGE 4- Usually, if the secondary current goes to zero, there is no reflected voltage across the primary side of the transformer, hence the magnetizing inductance of transformer begins to resonate with the output capacitance of the switches. This resonance between the switch capacitance and magnetizing inductance causes the voltage across the switch to swing to abnormal voltage levels causing switch stress for several cycles.

But, in the power electronic system topology configured according to the present invention, the secondary current has a continuous flow through the current sources CS1 and CS2 for power converters 1 and 2, therefore, very less resonant oscillations are observed before S1 comes back to action again. Consequently, this reduces the switch stress and considerably improves the power transfer to the connected load.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The integrated power conversion system configured in accordance with the present invention has the following advantages:

COMMERCIAL ADVANTAGES

• System can be used to develop a new range of hybrid electric vehicles.

• Reduction in power electronic switch stresses and losses, leading to designers having more space leverage to put in other stuff.

COST ADVANTAGES

• System configuration can be utilized in electric hybrid applications for smoother power conversion.

• Reduced cooling unit size resulting in lower manufacturing costs.

• Lesser equipment failure, leading to substantial economic benefits

OTHER ADVANTAGES

• Compact structure

• Reduced switching losses

• Less stress as compared to conventional topologies

• Higher efficiency

• Provides the maximum duty cycle

• Increased individual module level output, if used

• Useful for hybrid renewable energy application, such as HEVs and EVs.

• Resonance oscillation cycles dampened out to just a few rounds.

• Lighter magnetics design of the power transformer.

• Continuous supply of power to the connected load due to the maximum duty cycle.

• Very high performance and reliability of the vehicle.

• Smooth energy transfer due to the usage of current sources keeping the flow of secondary current and as the capacitances, inductances are aligned

• Option for selecting semiconductor switches for less voltage levels due to lower stress factors.

• Effective parallel connection of the power converters serves as a bridge between multiple DC power sources to the connected load to facilitate smart operation according to the supply and load variations.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

In the claims and the description, the terms “containing” and “having” are used as linguistically neutral terminologies for the corresponding terms “comprising”.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention. Furthermore, the use of the term “one” shall not exclude the plurality of such features and components described.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention.

The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

In the previously detailed description, different features have been summarized for improving the conclusiveness of the representation in one or more examples. However, it should be understood that the above description is merely illustrative, but not limiting under any circumstances. It helps in covering all alternatives, modifications and equivalents of the different features and exemplary embodiments.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention.

These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

The exemplary embodiments were selected and described in order to be able to best represent the principles and their possible practical application underlying the invention. Many other examples are directly and immediately clear to the skilled person because of his/her professional knowledge in view of the above description. Thereby, the skilled persons can optimally modify and use the invention and its different exemplary embodiments with reference to the intended use.