WO2023224495A1 - Variable battery energy management system - Google Patents

Abstract

A variable battery system is disclosed. The system comprises a number of DC sources which by/via control signal will produce wavelets, and a (centralized) control system arranged for individual (monitoring and) control of each DC source cell.

Description

Title

VARIABLE BATTERY ENERGY MANAGEMENT SYSTEM

1. Field of the invention .1. The present invention relates to a variable energy management system and a corresponding battery system (the "VBEMS"). Moreover, the invention also relates to a method for using the VBEMS in a number of applications. .2. Wavelet is an expression used to describe any waveform including AC and DC signals that are possibly being synthesized/modulated/regulated from a VBEMS using real time cell switching arrangement and PWM. .3. The invention relates to the modulation of wavelets from a battery energy unit and the specific MOSFET activation sequence to ensure that the system maintains an uninterrupted current path from the battery system during any cell switching in real time.

2. Background of the invention .1. There already exist solutions for connecting battery systems to the power grid. Common to these battery systems is a dedicated direct current ("DC") bus (a circuit or protocol that serves as a common communications pathway shared by several components and which uses a direct current, voltage level as a reference), which interacts with an AC grid through an inverter. Traditional battery systems consist of three separate functions: 1) charger, 2) battery management system (BMS), and 3) inverter. .2. These traditional battery systems have, among other things, limited control over the amount of charge. Charging of the battery system is performed at a fixed rate until it is fully charged. The expected system losses of traditional battery systems are up to 15%. Further, traditional battery systems require matching of cells so that the initial system is made up of identical cells. As the cells age, they typically evolve and degrade at different rates even if the initial selection is done very carefully. Therefore, at any given time the weakest cell(s) will determine the capacity of the battery system. This invention, the VBEMS, transfers monitoring and control for charge and discharge from a system level to each individual cell, or batches of cells. Artificial intelligence ("Al") or similar smart control based on lang term monitoring of the cells' thermal behavior during charge and discharge, along with continuous monitoring of internal resistance and cell capacity, allows for accurate state-of- health ("SoH") and state-of-charge ("SoC") calculations that will adapt to the cell's degradation over its lifetime. Adjusting the load and charge patterns accordingly allows for longer battery life by ensuring parallel and identical cell degradation, even if cells are of unequal quality. For all half H-bridge MOSFET designs, the switching sequence is critical and which to an extent can be divided into two opposite switching strategies; break- before-make and make-before-break.

Due to a certain slew rate in the MOSFET switch-on and switch-off sequences, most switching designs are using high precision timing in order to have an almost simultaneous crossover in the turn-on of one transistor while simultaneously turning-off the other transistor. Manufacturing variations for MOSFETs makes it a bit difficult to have exactly that same gate capacity for all MOSFETs and by that making it difficult to find individual optimal timing in crossover for a large set of transistors as they will have some deviation in slew rate caused by production tolerances.

For this invention the design is using two opposite (mirrored connected) MOSFETs pr switch to make a solid state switch which can be fully opened or fully closed independent upon a positive and negative polarity being applied. If this configuration had been using only one MOSFET pr switch then it would have been able to open and close completely for one polarity, but being open or having the body diode activated and being conductive through the body diode for the other polarity. I.e, for the other polarity not being able to fully close.

This invention is actively using the conducting body diode during the cell switching sequence to maintain stable conductivity and thereby maintaining the current flow in the battery system at all time and including the cell switching sequence. Summary of the invention The invention seeks to provide a single system which has same or all the functionalities of a traditional battery system, consisting of 1), charging 2) BMS, and 3) inverter, but with additional new functionalities concerning the cell switching sequences and that process active use of MOSFET body diode in reverse polarity. Due to individual cell control that optimize charge/discharge patterns for each individual cell, the costs can be reduced and the reliability increased. Cells and modules of differing quality can be used in the same system while cell cycle life and system life can be extended. Hence, cells can individually be charging or discharging in any instant. By arranging the battery cells in an arrangement, the voltage, phase angle and current can be very accurately controlled, and switching losses can be minimized. Due to the individual cell control the system can also utilize battery cells with different quality for the utilization of second hand cells and out of specification new cells in new applications. Total system losses are typically very low across the entire operational range of the system. Due to the individual cell control, the system can change behavior to match the desired application in software without any change in hardware. The charge rate can further be adjusted to optimally fit peak shaving requirements or optimize charging based on individual needs of each cell over the timeframe that is available to fully charge the system. The system may need to recharge in eight (8) hours during the weekdays while it can use twenty-four (24) hours to fully charge over the weekend, further minimizing the wear and tear on the individual cell. Furthermore, full cell diagnostics can be conducted on an individual cell level as if it was in a laboratory environment during normal system operation. Moreover, the system can bypass cells and therefore can be designed with built in redundancy where one or more extra cells are added to the system to allow chosen cells to break down without affecting the operation of the system. Due to the invention's design, several additional benefits are intrinsic to the system. The invention's ability to adapt as an individual system or in conjunction with other units allows it to operate with multiple component failures that makes it ideal for applications demanding high reliability. The invention's ability to generate and distribute wavelets to and from individual cells or other attached DC sources such as solar panels, capacitors, fuel cells or via the power interphase, allows the invention to cater to the needs of individual cells and to possibly constantly maintain cell balance regardless of cell health, cell state of charge and workload in real time during normal operations. Optionally, the battery energy control system comprises a string control system arranged to control each string. Optionally, each DC cell can consist of a regulator arranged to control charging and discharging current of the DC cell under control of the control system, alternatively each regulator comprises both a series switch for each cell and a parallel switch for each cell or the entire string. Optionally, a single string or a number of parallel strings are arranged to represent a (1) phase of an AC grid, and further optionally the AC grid is either in single phase configuration or a three (3) or more phase configuration in a delta or star configuration. Optionally, the regulators are arranged to allow the DC cells to interact with the grid in such way that the individual cell's potential compared to the grid can be offset in any instance, and further, the invention is arranged in such way that a lower potential will result in charging the string from the grid and a higher potential will result in a discharge to the grid. Optionally, the control systems of the invention are arranged to monitor characteristics of each cell in time intervals. Based on the characteristics and current application of the battery system, this will optimize control of the system, and further optionally the monitoring comprises measuring current, voltage and temperature for each DC cell. Optionally, the system is arranged for changing topography of the immediate connections between the individual DC cells in or out in real time, rearranging the structure of the battery in real time, and further optionally the changing topography comprises switching in and out of individual DC cells including, but not limited to, bypassing cells. Optionally, the changing topography comprises flexibly substituting DC cells by redundant DC cells. Optionally, the invention comprises an Al system arranged to learn the present characteristics of each cell and contribute to optimizing the control of the system in view of the current application of the system. Optionally, the cell charging is of any types: continuous, pulse, burp or sinusoidal. Optionally, the system comprises an unfolder arranged for changing polarity of the combined output wavelets to match the phase of a power interface. Optionally the system comprises predictive analysis that makes the system actively counteract unwanted noise and behaviors on the power interface. Another aspect of the invention is a method of using the VBEMS, as described above, for any of the following applications:

- Frequency Regulation for keeping frequency within its defined tolerance range,

- Voltage Regulation for keeping the voltage within its defined tolerance range,

- Voltage conversion, changing the input and output voltage on parallel power interfaces,

- Transfer energy between two (2) different power interfaces with different voltages and/or frequencies,

- Fast Reserve for keeping production and consumption balanced, - Transmission and Distribution Deferral for postponing grid investments due to impending overload of components,

- Black Start for assisting the grid in coming back online after an outage,

- Asset Optimization for increasing thermal power plants' reaction time,

- Redispatch for preventing bottlenecks,

- Motor driver,

- Renewable Energy integration for enabling integration of renewable energy,

- Backup Power for secondary power supply in case of outages,

- Distributed large scale energy storage,

- increased PV1 Self-consumption for becoming energy independent,

- Energy Arbitrage for buying electricity when it is cheap and using it when it is expensive,

- Grid Rental Fee Reduction for reducing the power component of the grid rental fee, and

- Peak Shaving for reducing power consumption peaks. 22. The embodiments of the invention are susceptible to being combined in various combinations - commonly called application stacking.

Description of the diagrams

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1 A is an illustration of an embodiment of a storage cell controller system pursuant to the present invention,

FIG 1 B is an illustration of two serially connected and mirrored MOSFETs highlighting the body diode. This is the actual implementation of for the switching states described in;

FIG 1 C is describing the different switching states for a pair of two serially connected and mirrored MOSFETs as shown in FIG 1 B. Switching states (a) and (e) are both showing an open circuit with forward and reversed polarity. Switching state (b) and switching state (d) are showing active body diode in forward and reversed polarity. Switching state (c) is showing a conducting bidirectional connection. (11) is an open switch equivalent, (12) is a closed switch equivalent and (20) and (21) are showing active body diodes in forward and reversed polarity configurations.

FIG. 1 C is an illustration of the different stages in a cell switching process from full conducting bi-directional switch connection to open circuit for a serially connected a mirrored par of MOSFETs.

FIG. 2 is a representation of synthesis of an output wavelet representing a sinusoidal AC signal.

FIG. 3 is an illustration of an embodiment of a complete system pursuant to the present invention,

thereby reducing a need for output filtering to remove harmonic content present in the output from the system;

Description of embodiments of the invention

For all half H-bridge MOSFET designs, the switching sequence is critical which to an extent can be divided into two switching principles; break-before-make and make-before- break. Due to a certain slew rate in the MOSFET switch-on and switch-off sequences of most designs are using high precision timing in order to have an almost simultaneous crossover in the turn-on of one transistor while simultaneously turning-off the other transistor, but manufacturing variations for MOSFETs makes it a bit difficult to have exactly that same gate capacity for all MOSFETs and by that making it difficult to find individual optimal timing for crossover for a large set of transistors as they will have some deviation in slew rate.

FIG 1A shows a principal sketch for a simple variant of a connection diagram where a single battery cell can be connected or bypassed. Two and two MOSTFETs in series with mirrored mounting are forming a path through the battery cell and a similar set of transistors forming the bypass path.

For this invention the design is using the two opposite (mirrored connected) MOSFETs pr switch to make a solid state switch that can be fully open or fully closed independent upon where a positive and negative polarity is being applied seen from the terminals of FIG 1A. The change in polarity will be an effect of the difference in operational mode distinguishing charging from discharging. If this configuration had been using only one MOSFET pr switch equivalent rather than two opposite connected in series, then each switch would have be able to open and close completely for one polarity, but being open or having the body diode activated and being conductive through the body diode for the other polarity. I.e, for the other polarity not being able to fully close/disconnect.

A switching design using a break-before-make principle in a battery system will break a high current circuitry which can result in particularly high voltages being generated in the same way as seen in a coil is designed to make sparks due to the induced magnetic field from the high current and which can potentially destroy the electronics.

If instead using of a make-before-break principle, this could, in turn, result in a high circular short-circuit current from the active cell and via the bypass connection as shown in FIG 1 A and overheat the MOSFETs as their internal low but still measurable resistance in the MOSFETs for a short period of time will convert this energy to heat. And then after releasing the high current that flows in the feedback loop, then once again experience a smaller coil effect from the magnetic effect around conductors in the busbar system caused by the previous high current.

The main principle of the invention involves using the body diode for one of the two transistors as an active conductor for a very short period of time during a two-step switching sequence for two serially connected and mirrored transistors in a pair. This means that the transistor is actually open (i.e. deactivated from the gate signal), but since it operates with reverse voltage compared to how MOSFET are normal operated, the body diode will become active, and act as a serial resistance with a voltage drop in the system for an intermediate time/step of the switching cycle. This will reduce the coil effect.

The switching process for two opposite transistors in a pair will then take place in a two- stage process as described in A and B.

For cell switching to other cell or to a bypass connection or from a bypass to a cell or to another bypass connection the process will be as described in C.

A:

For transmission from an inactive/open connection, FIG 1 C switching state (a) or switching state (e), (being equivalent to a switch in the open position) to an active stage, FIG 1 C switching state (c) (equivalent to a switch in the conducting position):

1 . First activate the transistor in the right direction, where the body diode is still active, FIG 1 C, switching state (b) or switching state (d).

2. Activate the transistors that are reversed so that the body diode is deactivated. FIG 1 C switching state (c).

B:

For transmission from active/conducting stage, FIG 1 C switching state (c), (being equivalent to a switch in the conducting position) to a deactivated position, FIG 1C switching state (a) or switching state (e), (being equivalent to a switch in the open position)

1 . Deactivate the transistor that is reversed so that the Body diode becomes active for a short period, FIG 1 C state (b) or switching state (d)

2. Deactivate the transistor that is in the correct direction, FIG 1 C switching state (a) or switching state (e)

C:

For two or more switch equivalents, each being a set of opposite mounted transistors corresponding to a bi-directional switch, both switches as described in FIG 1 A for the two bidirectional switch, one going through the battery cell and the other being a bypass connection, the bi-directional switches shall both be in the transition phase simultaneously as shown FIG 1 C switching state (b) or switching state (e) during the switching transition.

Claims

CLAIMS It is hereby claimed:

1. A distributed variable battery (energy management) system, where the system comprises:

- a plurality of DC sources controlled for charge and discharge via a distributed set of uniform building blocks, actively using the MOSFET body diodes in the switching sequences, enabling real time programmable battery topography, each DC source is operable to be charged and discharged via a control signal to produce wavelets; and

- a distributed control system arranged for individual control of each DC source, at any instant for selectively combining wavelets across the system.

2. The system according to claim 1 , further comprising a number of DC energy cells wherein each energy cell is operable to produce energy wavelets, and where the system is arranged to selectively combine wavelets, generating a composite synthesized power output from the system.

3. The system according to claim 1 or 2, further comprising a number of battery cells, in parallel grids where each battery cell is operable to produce the wavelet, and where the system is arranged to selectively combine wavelets generating different simultaneous synthesized output voltages and/or frequencies from the system.

4. A variable battery system comprising:

- a plurality of DC sources controlled for charge and discharge via a distributed set of uniform building blocks, actively using the MOSFET body diodes in the switching sequences, enabling real time programmable battery topography, each DC source is operable to be charged and discharged via a control signal to produce wavelets; and

- a distributed control system arranged for individual control of each DC source, at any instant for selectively combining wavelets across the system; wherein the battery control system comprises a string control system arranged to control each string. The variable battery system according to claim 4, wherein each DC cell comprises a linear regulator arranged to control charging and discharging current of the DC cell under control of the control system. The variable battery system according to claim 5, wherein each linear regulator comprises both a series switch for each cell and a parallel switch for the entire string. The variable battery system according to one of the claims 3 to 6, wherein a single string or a number of parallel strings are arranged to represent a phase of an AC grid. The variable battery system according to claim 7, wherein the AC grid is either in single phase configuration or a 3 or more phase configuration in delta or star configuration. The variable battery system according to claim 8, wherein the linear regulators are arranged to allow the DC cells to interact with the grid in such a way that the individual cell's potential compared to the grid can be offset in any instance. The variable battery system according to claim 9, arranged such that a lower potential will result in charging the cells from the grid and higher potential will result in a discharge to the grid. The variable battery system according to one of claims 4-9, wherein the centralized control system is arranged to monitor characteristics of each cell for each clock pulse, and based on the characteristics and current application of the system, optimize control of the system. The variable battery system according to claim 11 , wherein the monitoring comprises measuring current, voltage and temperature for each DC cell. The variable battery system according to claim 12, wherein the distributed battery control system is arranged for each individual DC cell in real time to estimate State of Charge and State of Health, and use it when optimizing control of the system. The variable battery system according to one of the claims 11 to 13, wherein the system is arranged for changing topography of individual DC cells by switching individual cells in or out in real time re-building the battery. The variable battery system according to claim 14, wherein the changing topography comprises switching in and out of individual DC cells including, among other things, bypassing cells. The variable battery system according to claim 14 or 15, wherein the changing topography comprises flexibly substituting DC cells by redundant DC cells. The variable battery system according to one of the claims 11 to 16, wherein the system comprises an artificial intelligence system arranged to learn the present characteristics of each cell and contribute to optimizing the control of the system in view of current application of the system. The variable battery system according to one of the claims above, wherein the cell charging is of any of the following types: continuous, pulse, burp and sinusoidal, or continuously changing between these types. The variable battery system according to one of the claims above, further comprising an unfolder arranged for changing polarity of the combined output wavelets to match the phase of a connected power interface. A method of using the variable battery system according to any of the claims 1 to

19 for at least one of the following applications, or a simultaneous combination of these:

- frequency regulation for keeping frequency within its defined tolerance range,

- voltage regulation for keeping the voltage within its defined tolerance range,

- voltage conversion, changing the input and output voltage on parallel power interfaces,

- transfer energy between to different power interfaces with different voltages and/or frequencies,

- fast reserve for keeping production and consumption balanced,

- transmission and distribution deferral for postponing grid investments due to impending overload of components,

- black start for assisting the grid in coming back online after an outage,

- asset optimization for increasing thermal power plants' reaction time,

- redispatch for preventing bottlenecks,

- motor driver,

- renewable energy integration for enabling integration of renewable energy,

- backup power for secondary power supply in case of outages,

- distributed large scale energy storage,

- increased pv1 self-consumption for becoming energy independent,

- energy arbitrage for buying electricity when it is cheap and using it when it is expensive,

- grid rental fee reduction for reducing the power component of the grid rental fee, and

- peak shaving for reducing power consumption peaks.