Description:TITLE OF THE INVENTION: AN APPARATUS FOR PARALLEL-CONNECTED ENERGY STORAGE SYSTEM STRINGS ACTIVE BALANCING
FIELD OF THE INVENTION
The present disclosure is generally related to energy storage systems of vehicles. The present disclosure is particularly related to energy storage system strings active balancing. The present disclosure is more particularly related to an apparatus, for: parallel-connected energy storage system strings active balancing, in real time.
BACKGROUND OF THE INVENTION
To fulfil the energy and power requirements of vehicles, a large number of cells are connected in series and/or in parallel configurations within an energy storage system (ESS). For example, in order to meet voltage requirements, the cells are connected in series, whereas the cells are connected in parallel to meet ampere hour requirements. However, it is recommended to avoid more numbers of parallel cell connections due to inconsistencies between the cells. Further, it becomes more severe with the aging of the cells and operating conditions.
In high-energy vehicles, energy storage system strings are connected in parallel to meet the ampere hour rating. In each string, several battery packs combining battery modules are connected in series to meet the voltage requirement of the energy storage system. However, with the increase in the energy and power requirements, the problem of charge imbalance in the energy storage system strings becomes significant, due to which the voltage across energy storage system strings gets mismatched. Hence, there would be a chance of a high flow of circulating current between the energy storage system strings, and it may increase the temperature that can lead to thermal runaway.
In the past few years, a few techniques, such as a passive balancer with a bleeder resistor and an active balancer, have been developed to control the energy storage system string imbalance issue. In the passive balancer (EP0814556B1) technique, the energy of the cell with a high charge is dissipated across the bleeder resistor to match the state of charge (SOC) or voltage levels of the cells that are connected in series. Whereas, in the active balancer (US20070216368A1) technique, the excess energy from the cell with higher SOC or voltage is transferred to the cell with lower SOC and voltage more effectively.
In high-energy vehicles with parallel-connected energy storage system strings, balancing is required both during installation and in real-time operations. Though there are few techniques available to perform the balancing in offline mode to mitigate the balancing issue, said techniques cannot resolve the balancing issue during real-time operations, necessitating requirement of active real-time balancing of energy storage system string in order to prevent circulating currents under no-load conditions
In the high-voltage battery packs with parallel-connected modules, balancing is required both during installation and in real-time operation. While there are few offline balancing systems already available to mitigate initial imbalances, but they cannot fully resolve dynamic imbalances during real-time operation, necessitating requirement of active real-time balancing in order to prevent circulating current within the energy storage system under no-load conditions.
Generally, during the charging of the ESS with imbalance strings, a charger is allowed to charge the low voltage and/or low SOC strings first till the voltage and/or SOC will not be equal to the high voltage string. Hence, the fast charging of the ESS with imbalanced strings cannot be done.
Further, under no-load conditions, the level of circulating current can be significantly high to affect performance of the energy storage system during real-time applications. Moreover, imbalance issues in the energy storage system string can affect the capacity of the energy storage system during charging and discharging. For example, during discharging, the energy storage system string with lower SOC or lower voltage will first reach the end-of-discharge condition. Similarly, during charging, the energy storage system string with higher SOC or higher voltage will first reach to end-of-charge condition and stop charging. As a result, the energy storage system cannot be utilised to its full capacity. On the other hand, high circulating currents can trigger overcurrent protection and halt the operation.
Currently, there is no comprehensive solution available for mitigating issues of energy imbalance in parallel-connected energy storage system strings, during charging and/or discharging of the vehicle, in real time.
There is, therefore, a need in the art, for: an apparatus, for parallel-connected energy storage system strings active balancing, in real-time, which overcomes the aforementioned drawbacks and shortcomings.
SUMMARY OF THE INVENTION
An apparatus, for parallel-connected energy storage system strings active balancing, in real-time, is disclosed. Said apparatus broadly comprises: an at least an energy storage system; an at least an energy storage system string balancing member; and an at least a monitoring member.
Said at least one energy storage system comprises a plurality of energy storage system packs. Each energy storage system pack among the plurality of energy storage system packs is connected with an adjacent energy storage system pack among the plurality of energy storage system packs through a respective energy storage system string among the plurality of energy storage system strings, in parallel
Said at least one monitoring member is disposed inside an at least an energy storage system, and is configured to sense voltage and/or State of Charge of each energy storage system string among the plurality of energy storage system strings continuously, in real-time, with the sensed data being transmitted to the at least one energy storage system string balancing member.
The at least one energy storage system string balancing member broadly comprises: a plurality of balancer units; and an at least an energy storage system balancer controller.
Said plurality of balancer units is communicatively associated with the at least one energy storage system balancer controller.
Each balancer unit among the plurality of balancer units is disposed between a pair of energy storage system strings among the plurality of energy storage system strings.
In an embodiment, each balancer unit among the plurality of balancer units broadly comprises: a first control switch; a second control switch; a diode; an inductor; and a resistor.
In an embodiment, said first control switch and said second control switch are Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) or Insulated Gate Bipolar Transistors (IGBTs).
In an embodiment, said diode is a Schottky Diode or the like with low forward voltage drop (for example, between about 0.3V and about 0.5V).
In an embodiment, said inductor is a Ferrite Core Inductor (for example, between about 50µH and about 500µH).
In an embodiment, said resistor is a Wire-wound Power Resistor (for example, between about 0.1Ω and about 10Ω).
The at least one energy storage system balancer controller is configured to balance the voltage and/or State of Charge imbalance in the plurality of energy storage system strings, with the help of the plurality of balancer units.
Said at least one energy storage system balancer controller broadly comprises: an at least a load status monitoring member; an at least a signal comparator member; and an at least a control signal generator.
The at least one load status monitoring member is configured to control the first control switch based on a load status of the at least one energy storage system.
The at least one signal comparator member is configured to control the second control switch based on the level of: voltage and/or State of Charge imbalance, in the plurality of energy storage system strings.
The at least one control signal generator is configured to generate control signals for controlling said first control switch and said control switch.
The method of working of the apparatus is also disclosed.
The disclosed apparatus offers at least the following advantages: is simple in construction; is cost-effective; effectively controls energy imbalance issues in real-time; reduces the charging time due to energy imbalance; offers increased energy efficiency; improves serviceability; and reduces field issues due to energy imbalance.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates an apparatus for parallel-connected energy storage system strings active balancing, in real-time, in accordance with an embodiment of the present disclosure;
Figure 2 illustrates a plurality of energy storage packs connected with strings within an at least one energy storage system, in accordance with an embodiment of the present disclosure;
Figure 3 illustrates a balancer unit and an at least one energy storage system string balancing controller of an apparatus for parallel-connected energy storage system strings active balancing, in real-time, in accordance with an embodiment of the present disclosure;
Figure 4 illustrates an at least one energy storage system string balancer controller of an apparatus for parallel-connected energy storage system strings active balancing, in real-time, in accordance with an embodiment of the present disclosure; and
Figure 5 is a flow chart illustrating a method of working of an apparatus for parallel-connected energy storage system strings active balancing, in real-time, in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF THE INVENTION
Throughout this specification, the use of the words “comprise” and “include”, and variations, such as “comprises”, “comprising”, “includes”, and “including”, may imply the inclusion of an element (or elements) not specifically recited. Further, the disclosed embodiments may be embodied, in various other forms, as well.
Throughout this specification, the use of the word “apparatus” is to be construed as: “a set of technical components (also referred to as “members”) that are communicatively and/or operably associated with each other, and function together, as part of a mechanism, to achieve a desired technical result”.
Throughout this specification, the use of the words “communication”, “couple”, and their variations (such as communicatively), is to be construed as being inclusive of: one-way communication (or coupling); and two-way communication (or coupling), as the case may be, irrespective of the directions of arrows, in the drawings.
Throughout this specification, the use of the word “balancing”, and its variations, is to be construed as being inclusive of: “equalising”, “matching”, and/or the like.
Throughout this specification, the use of the word “vehicle”, and its variations, is to be construed as being inclusive of: “commercial electrical vehicles (CEV)”. A person skilled in the art will appreciate the fact that the use of the word “vehicle” may also include: “other electric vehicles; hybrid electric vehicles; and/or the like”.
Throughout the specification, the use of the acronym “ESS” is to be construed as “Energy Storage System”.
Throughout the specification, the acronym “ESS” and the phrase “Energy Storage System” are used interchangeably.
Throughout this specification, the use of the word “Energy Storage System”, and its variations, is to be construed as being inclusive of: “lithium-ion battery system”, “battery” and/or the like.
Throughout this specification, where applicable, the use of the phrase “at least” is to be construed in association with the suffix “one” i.e. it is to be read along with the suffix “one”, as “at least one”, which is used in the meaning of “one or more”. A person skilled in the art will appreciate the fact that the phrase “at least one” is a standard term that is used, in patent specifications, to denote any component of a disclosure, which may be present (or disposed) in a single quantity, or more than a single quantity.
Throughout this specification, where applicable, the use of the phrase “at least one” is to be construed in association with a succeeding component name.
Throughout this specification, the use of the word “plurality” is to be construed as being inclusive of: “at least one”.
Throughout this specification, the words “the” and “said” are used interchangeably.
Throughout this specification, the word “sensor” and the phrase “sensing member” are used interchangeably. The disclosed sensing members may be of any suitable type known in the art.
Throughout this specification, the phrases “at least a”, “at least an”, and “at least one” are used interchangeably.
Throughout this specification, the disclosure of a range is to be construed as being inclusive of: the lower limit of the range; and the upper limit of the range.
Also, it is to be noted that embodiments may be described as a method. Although the operations, in a method, are described as a sequential process, many of the operations may be performed in parallel, concurrently, or simultaneously. In addition, the order of the operations may be re-arranged. A method may be terminated, when its operations are completed, but may also have additional steps.
An apparatus (100), for parallel-connected energy storage system strings active balancing (hereafter also referred to as “apparatus”), in real-time, is disclosed. In an embodiment, as illustrated in Figure 1, said apparatus (100) broadly comprises: an at least an energy storage system string balancing member (2000); and an at least a monitoring member (3000).
In another embodiment of the present disclosure, said at least one energy storage system string balancing member (2000) and said at least one monitoring member (3000) are communicatively associated with an at least an energy storage system (1000).
As illustrated in Figure 2, said at least one energy storage system (1000) broadly comprises a plurality of energy storage system packs (for example, ESS pack – 1 to ESS pack – N). Said plurality of energy storage system packs are connected (or coupled) by a plurality of energy storage system strings (for example, ESS string – 1 to ESS string – M, as illustrated in Figure 1).
In yet another embodiment of the present disclosure, each energy storage system pack (1110) among the plurality of energy storage system packs is connected (or coupled) with an adjacent energy storage system pack (1110) among the plurality of energy storage system packs through a respective energy storage system string (1100) among the plurality of energy storage system strings, in parallel.
The at least one monitoring member (3000) is disposed (or mounted, or installed, or positioned) inside the at least one energy storage system (1000), and is configured to monitor (or sense) voltage and State of Charge of each energy storage system string (1100) among the plurality of energy storage system strings continuously, in real-time, with the sensed data being transmitted to the at least one energy storage system string balancing member (2000).
As illustrated in Figure 1, said at least one energy storage system string balancing member (2000) broadly comprises: an at least an energy storage system balancer controller (2200) and a plurality of balancer units (for example, Balancer Unit – 1 to Balancer Unit - M).
In yet another embodiment of the present disclosure, each balancer unit (2100) among the plurality of balancer units is disposed (or mounted, or installed, or positioned) between a pair of energy storage system strings among the plurality of energy storage system strings. Said plurality of balancer units is communicatively associated with the at least one energy storage system balancer controller (2200).
As illustrated in Figure 3, each balancer unit (2100) among the plurality of balancer units broadly comprises: a first control switch (2110); a second control switch (2120); a diode (2130); an inductor (2140); and a resistor (2150).
In yet another embodiment of the present disclosure, said first control switch (2110) and said second control switch (2120) are Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) or Insulated Gate Bipolar Transistors (IGBTs).
In yet another embodiment of the present disclosure, said diode is a Schottky Diode or the like with low forward voltage drop (for example, between about 0.3V and about 0.5V).
In yet another embodiment of the present disclosure, said inductor is a Ferrite Core Inductor (for example, between about 50µH and about 500µH).
In yet another embodiment of the present disclosure, said resistor is a Wire-wound Power Resistor (for example, between about 0.1Ω and about 10Ω).
As illustrated in Figure 3, said at least one energy storage system balancer controller (2200) broadly comprises: an at least a load status monitoring member (2210); an at least a signal comparator member (2220); and an at least a control signal generator (2230).
The at least one energy storage system balancer controller (2200) is configured to balance the voltage and/or State of Charge (SOC) imbalance in the plurality of energy storage system strings, with the help of the plurality of balancer units, by generating control signals through the control signal generator (2230), during no-load real-time operation, to enhance the performance of the at least one energy storage system (1000).
In yet another embodiment of the present disclosure, said at least one load status monitoring member (2210), said at least one signal comparator member (2220), and said at least one control signal generator (2230) are associated with each other.
In yet another embodiment of the present disclosure, said at least one load status monitoring member (2210) is configured to detect (or sense, or monitor) a load status of the at least one energy storage system (1000).
In yet another embodiment of the present disclosure, said at least one signal comparator member (2220) is configured to detect (or sense, or monitor) the difference in the voltage and/or SOC (ΔSOC_string and/or ΔV_string) of each energy storage system string (1100) among the plurality of energy storage system strings.
Said ΔSOC_string and ΔV_string are calculated using the following formula:
ΔSOC_string = SOCmax − SOCmin
Where, SOCmax and SOCmin represents the highest and lowest SOC levels, respectively, among the plurality of energy storage system strings.
ΔV_string = Vmax − Vmin
Where, Vmax and Vmin represents highest and lowest voltages, respectively, among the plurality of energy storage system strings.
Said at least one load status monitoring member (2210) is configured to control the first control switch (2110) based on the load status of the at least one energy storage system (1000), by generating control signals through the control signal generator (2230), and said at least one signal comparator member (2220) is configured control the second control switch (2120) based on the level of: voltage and/or State of Charge (SOC) imbalance, in the plurality of energy storage system strings.
Method of working of the apparatus (100) shall now be explained in detail with the help of Figure 5.
In step S101, the at least one monitoring member (3000) continuously monitors and collects, in real-time, voltage and State of Charge (SoC) of each energy storage system string (1100) among the plurality of energy storage system strings connected in parallel, along with the load status of the at least one energy storage system (1000).
In yet another embodiment of the present disclosure, the load status is “Yes”, if the load is connected with the at least one energy storage system (1000) [causing the at least one ESS (1000) to discharge], and the load status is “No”, if the load is not connected with the at least one energy storage system (1000).
In step S102, the plurality of balancer units (2100) is switched-off, if the load status is “Yes”, and returns back to step S101. Moves on to the next step (S103), if the load status is “No”.
In step S103, the difference in the voltage and/or SOC (ΔSOC_string and/or ΔV_string) of each energy storage system string (1100) among the plurality of energy storage system strings is compared with a threshold limit (i.e. threshold voltage and a threshold SoC).
In yet another embodiment of the present disclosure, the threshold voltage ranges between about 50mV and about 200mV per energy storage system string (1100).
In yet another embodiment of the present disclosure, the threshold SoC ranges between about 2% and about 5% (i.e. 0.02 to 0.05 in SOC scale).
If ΔSOC string and/or ΔV string values are within the limit (i.e. no imbalance), moves on to step S101, after switching-off the plurality of balancer units (if any of the balancer unit (2100) among the plurality of balancer unit is switched-on).
If ΔSOC_string and/or ΔV_string are above the threshold limit (i.e. imbalance), moves on to the next step (S104).
In step S104, the plurality of balancer units is switched-on, and the balancing process is initiated. One or more of the respective balancer units is switched-on, depending of the location of imbalance in the plurality of energy storage system strings.
In step S105, when a balancer unit (2100) is switched-on, the first control switch (2110) is set to position P2 by a first control signal received from the at least one control signal generator (2230), based on the load status.
Then in step S106, the second control switch (2120) position is controlled based on the level of voltage and/or State of Charge (SOC) imbalance in the plurality of energy storage system strings by a second control signal received from the at least one control signal generator (2230). Where the second control signal is generated by at least one control signal generator (2230) based on the ΔSOC_string and/or ΔV_string values.
A person skilled in the art will appreciate the fact that the control signals can be generated in various method, such as width-based method, proportional integral batted method, and/or the like. The main purpose of generating control signals is to maintain the circulating current within safe limits during the balancing of the imbalance in the plurality of energy storage system strings.
When the first control switch (2110) is at the position P2, the plurality of energy storage system strings is connected through the inductor (2140) and the resistor (2150) that are connected in series, thereby limiting the circulating current during energy transfer between one energy storage system string among the plurality of energy storage system strings and another energy storage system string among the plurality of energy storage system strings.
Whereas, when the position of the first control switch (2110) is at P1, the balancer unit (2100) is disconnected, and the energy stored in the inductor (2140) is dissipated across the resistor (2150) through the diode (2130) that is connected in parallel.
The balancing of the plurality of energy storage system strings (1100) is continued until the ΔSOC _string values or ΔV _string values fall below the threshold limit.
The working of the apparatus (100) in respect of different positions of the first control switch (2110) and the second control switch (2120) are explained as follows:
Case 1: the first control switch (2110) at P1 and the second control switch (2120) at P2:
The first control switch (2110) is open, and disconnecting the balancer unit (2100). The second control switch (2120) is closed, and allowing energy flow between the plurality of energy storage system strings through the inductor (2140) and the resistor (2150). Energy balancing occurs at a controlled rate with limited circulating current.
Case 2: the first control switch (2110) at P2 and the second control switch (2120) at P1:
The first control switch (2110) is closed, and connecting the balancer unit (2100). The second control switch (2120) is open, and preventing direct energy flow between the plurality of energy storage system strings. The energy stored in the inductor (2140) is dissipated through the resistor (2150).
Case 3: the first control switch (2110) at P1 and the second control switch (2120) at P1:
Both the first control switch (2110) and the second control switch (2120) are open. The balancer unit (2100) is inactive.
Case 4: the first control switch (2110) at P2 and the second control switch (2120) at P2:
Both the first control switch (2110) and the second control switch (2120) are closed. Maximum energy flow between the plurality of energy storage system strings. Circulating current is limited by the combination of the inductor (2140) and the resistor (2150).
The disclosed apparatus (100) offers at least the following advantages: is simple in construction; is cost-effective; effectively controls energy imbalance issues in real-time; reduces the charging time due to energy imbalance; offers increased energy efficiency; improves serviceability; and reduces field issues due to energy imbalance.
A person skilled in the art will appreciate the fact that the apparatus, and its various components, may be made of any suitable materials known in the art. Likewise, a person skilled in the art will also appreciate the fact that the configurations of the apparatus, and its various components, may be varied, based on requirements.
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements, without deviating from the spirit and the scope of the disclosure, may be made, by a person skilled in the art. Such modifications, additions, alterations, and improvements should be construed as being within the scope of this disclosure.
 
LIST OF REFERENCE NUMERALS
100 – Apparatus for Parallel-Connected Energy Storage System Strings Active Balancing.
1000 - At Least One Energy Storage System
1100 – Energy Storage System String
1110 – Energy Storage System Pack
2000 – At Least One Energy Storage System String Balancing Member
2100 – Balancer Unit
2110 – First Control Switch
2120 – Second Control Switch
2130 – Diode
2140 – Inductor
2150 – Resistor
2200 – At Least One Energy Storage System Balancer Controller
2210 – At Least One Load Status Monitoring Member
2220 – At Least One Signal Comparator Member
2230 – At Least One Control Signal Generator
3000 – At Least One Monitoring Member , Claims:1. An apparatus (100), for parallel-connected energy storage system strings active balancing, in real-time, comprising:
an at least a monitoring member (3000) that is disposed inside an at least an energy storage system (1000), and is configured to sense voltage and State of Charge of each energy storage system string (1100) among the plurality of energy storage system strings continuously, in real-time, with the sensed data being transmitted to an at least an energy storage system string balancing member (2000), with:
said at least one energy storage system (1000) comprising a plurality of energy storage system packs, with:
each energy storage system pack (1110) among the plurality of energy storage system packs being connected with an adjacent energy storage system pack (1110) among the plurality of energy storage system packs through a respective energy storage system string (1100) among the plurality of energy storage system strings, in parallel; and
the at least one energy storage system string balancing member (2000) that comprises:
a plurality of balancer units, with:
said plurality of balancer units being communicatively associated with an at least an energy storage system balancer controller (2200);
each balancer unit (2100) among the plurality of balancer units being disposed between a pair of energy storage system strings among the plurality of energy storage system strings; and
each balancer unit (2100) among the plurality of balancer units comprising: a first control switch (2110); a second control switch (2120); a diode (2130); an inductor (2140); and a resistor (2150); and
the at least one energy storage system balancer controller (2200) that is configured to balance the voltage and State of Charge imbalance in the plurality of energy storage system strings, with the help of the plurality of balancer units, said at least one energy storage system balancer controller (2200) comprising:
an at least a load status monitoring member (2210) that controlling the first control switch (2110) based on a load status of the at least one energy storage system (1000);
an at least a signal comparator member (2220) that controlling the second control switch (2120) based on the level of: voltage or State of Charge imbalance, in the plurality of energy storage system strings; and
an at least a control signal generator (2230) that generating control signals for controlling said first control switch (2110) and said control switch (2120).
2. The apparatus (100), for parallel-connected energy storage system strings active balancing, in real-time, as claimed in claim 1, wherein: said first control switch (2110) and said second control switch (2120) are Metal-Oxide-Semiconductor Field-Effect Transistors or Insulated Gate Bipolar Transistors.
3. The apparatus (100), for parallel-connected energy storage system strings active balancing, in real-time, as claimed in claim 1, wherein: said diode (2130) is a Schottky Diode with low forward voltage drop.
4. The apparatus (100), for parallel-connected energy storage system strings active balancing, in real-time, as claimed in claim 1, wherein: said inductor (2140) is a Ferrite Core Inductor.
5. The apparatus (100), for parallel-connected energy storage system strings active balancing, in real-time, as claimed in claim 1, wherein: said resistor (2150) is a Wire-wound Power Resistor.