CN113629821B

CN113629821B - Energy storage system and control method thereof

Info

Publication number: CN113629821B
Application number: CN202111026301.8A
Authority: CN
Inventors: 孙维; 陈飞; 李鹏举; 陈晓光
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2024-04-12
Anticipated expiration: 2041-09-02
Also published as: CN113629821A

Abstract

The invention provides an energy storage system and a control method thereof, wherein a control unit can control each battery module to cut in or cut out a corresponding battery cluster when meeting corresponding preset conditions so as to adjust the currently accessed battery module in the battery cluster in real time, and further can enable each battery module to meet the corresponding preset conditions one by one, namely to achieve the same state, such as realizing SOC balance; and at the same time, no energy is wasted. And at least one buffer circuit is arranged in the energy storage system, so that voltage peaks caused by switching in or out any battery module in the corresponding battery cluster can be absorbed, namely energy impact caused by voltage abrupt change is absorbed, and further, the corresponding device is prevented from bearing larger voltage/current stress.

Description

Energy storage system and control method thereof

Technical Field

The invention relates to the technical field of power electronics, in particular to an energy storage system and a control method thereof.

Background

The battery cluster in the energy storage system is usually formed by connecting a plurality of battery modules in series; in the same battery cluster, the problem of unbalanced SOC (state of charge) of each battery module is unavoidable in the use process.

In order to solve the problem of unbalanced SOC of the battery module, the scheme commonly used at present is: the battery module with high energy is passively discharged through the resistor, so that the excessive energy is dissipated in the form of heat, and the energy of the battery module is kept consistent with that of the battery module with low energy.

But this solution dissipates the excess energy, resulting in a waste of energy.

Disclosure of Invention

In view of the above, the present invention provides an energy storage system and a control method thereof, so as to avoid energy waste while realizing SOC equalization of the battery module.

In order to achieve the above object, the embodiment of the present invention provides the following technical solutions:

the first aspect of the present invention provides an energy storage system comprising: the power converter comprises a control unit, at least one battery cluster, at least one buffer circuit and at least one power converter; wherein:

the battery cluster comprises a plurality of battery modules which are connected in series, and two ends of each battery module which are connected in series are used for being connected with the direct current buses of the corresponding power converter;

a bus capacitor is arranged between the anode and the cathode of the direct current bus;

the control unit controls each battery module to cut in or cut out the battery module from the corresponding battery cluster when the corresponding preset condition is met;

The buffer circuit is controlled by the control unit and is used for absorbing voltage peaks caused by switching in or out any battery module in the corresponding battery cluster.

Optionally, the buffer circuit includes: a controllable switch and a buffer device connected in parallel;

when the battery module is cut in or out in the corresponding battery cluster, the controllable switch is in an off state;

and when the voltage difference between the voltage of the corresponding battery cluster and the bus capacitor is smaller than a preset difference value, the controllable switch is in a closed state.

Optionally, the buffer device includes: resistance, or resistance and inductance connected in parallel.

Optionally, the buffer circuit is disposed on the dc bus, or the buffer circuit and the bus capacitor are connected in series between the positive electrode and the negative electrode of the dc bus.

Optionally, the battery module further includes: the battery comprises a battery body, a main loop on-off control circuit and a bypass on-off control circuit; wherein:

the battery body is connected with the anode and the cathode of the battery module through the main loop on-off control circuit;

the bypass on-off control circuit is arranged between the anode and the cathode of the battery module.

Optionally, the main loop on-off control circuit and the bypass on-off control circuit each include: a two-way unidirectional switch group; the two-way unidirectional switch group comprises: a charge switch and a discharge switch; the control unit controls the charging switch in the main loop on-off control circuit to charge the corresponding battery body, controls the discharging switch in the main loop on-off control circuit to discharge the corresponding battery body, controls the charging switch in the bypass on-off control circuit to realize a charging bypass for the corresponding battery body, and controls the discharging switch in the main bypass on-off control circuit to realize a discharging bypass for the corresponding battery body;

or,

and the main loop on-off control circuit and the bypass on-off control circuit both comprise: a single-path bi-directional switch; and the control unit controls the bidirectional switch in the main loop on-off control circuit to charge or discharge the corresponding battery body, and controls the bidirectional switch in the bypass on-off control circuit to realize a charging bypass or a discharging bypass of the corresponding battery body.

Optionally, the charging switch includes: a charging switch tube and a charging diode which is reversely connected with the body diode in the charging switch tube in series; the discharge switch includes: a discharge switch tube and a discharge diode which is reversely connected with the body diode in the discharge switch tube in series; the charging switch is reversely connected in parallel with the discharging switch;

or,

the charging switch comprises a charging switch tube, and the discharging switch comprises a discharging switch tube; the charging switch tube and the discharging switch tube are provided with body diodes which are connected in reverse series.

Optionally, a switch box is further disposed between each battery cluster and the corresponding power converter, and the switch box includes: and a main loop switch.

Optionally, the control unit is a battery management system BMS, and the BMS includes: the system comprises a system battery management unit SMU, battery cluster management units CMU of each battery cluster and battery management units BMU arranged in each battery module;

the SMU, the CMU and the BMU are in step-by-step communication connection;

the buffer circuit is controlled by the CMU corresponding to the battery cluster;

the CMU is communicatively coupled to the power converter.

Optionally, the power converter is a DCAC converter; or,

The power converters are DCDC converters, and each DCDC converter is connected with a power grid and/or a load through a corresponding DCAC converter.

The second aspect of the present invention also provides a control method of an energy storage system, which is applied to the control unit in the energy storage system according to any one of the paragraphs of the first aspect; the control method comprises the following steps:

s101, judging whether each battery module in a corresponding battery cluster of the energy storage system meets corresponding preset conditions or not;

if any battery module meets the corresponding preset condition, executing step S102;

s102, controlling the corresponding battery module to cut in or cut out of the battery cluster; meanwhile, a corresponding buffer circuit in the energy storage system is controlled to absorb voltage peaks caused when the corresponding battery module is cut in or cut out;

s103, judging whether the voltage difference between the battery cluster and the corresponding bus capacitor is within a preset voltage range;

if the voltage difference is within the preset voltage range, executing step S104;

s104, controlling the buffer circuit to stop absorbing the voltage spike.

Optionally, the preset condition is a cut-out preset condition or a cut-in preset condition; the buffer circuit includes: a controllable switch and a buffer device connected in parallel; and in the main loop on-off control circuit and the bypass on-off control circuit in the battery module, all include: a single-path bi-directional switch; then:

When the preset condition is the cut-out preset condition, step S102 includes: the two-way switch in the corresponding main loop on-off control circuit is controlled to be turned off, and the controllable switch is controlled to be turned off at the same time; then controlling the two-way switch in the corresponding bypass on-off control circuit to be conducted;

when the preset condition is the cut-in preset condition, step S102 includes: the two-way switch in the bypass on-off control circuit is controlled to be turned off, and the controllable switch is controlled to be turned off; and then controlling the conduction of the bidirectional switch in the corresponding main loop on-off control circuit.

Optionally, the preset condition is a cut-out preset condition or a cut-in preset condition; the buffer circuit includes: a controllable switch and a buffer device connected in parallel; the main loop on-off control circuit and the bypass on-off control circuit in the battery module comprise two-way unidirectional switch groups; then:

when the preset condition is the cut-out preset condition, step S102 includes: controlling the corresponding bypass on-off control circuit to be conducted, and simultaneously controlling the controllable switch to be disconnected;

when the preset condition is the cut-in preset condition, step S102 includes: controlling the on-off control circuit of the corresponding main loop to be conducted; and then controlling the corresponding bypass on-off control circuit to be turned off, and simultaneously controlling the controllable switch to be turned off.

Optionally, when the preset condition is the cut-out preset condition, in step S102, after controlling the corresponding bypass on-off control circuit to be on and controlling the controllable switch to be off, the method further includes: and controlling the on-off control circuit of the corresponding main loop to be turned off.

Optionally, the preset cutting condition is any one of the following:

when the battery cluster is charged, a first preset condition is cut out when the operation parameter of the corresponding battery module reaches a preset upper limit value;

when the battery cluster discharges, a second cutting-out preset condition that the operation parameter of the corresponding battery module reaches a preset lower limit value is met;

when the battery cluster is charged, a third cutting-out preset condition is met when the corresponding battery module is abnormal or fails;

when the battery cluster discharges, cutting a preset condition corresponding to the fourth abnormal or fault condition of the battery module;

the cutting preset condition is any one of the following conditions:

a first cut-in preset condition requiring recovery from the charge bypass state to the charge state;

a second cut-in preset condition is required to restore from the discharge bypass state to the discharge state.

Optionally, the main loop on-off control circuit and the bypass on-off control circuit in the battery module both comprise: charging switch tube and discharging switch tube, then:

When the preset condition is the first cut-out preset condition or the third cut-out preset condition, in step S102, the corresponding bypass on-off control circuit is controlled to be turned on, and the controllable switch is controlled to be turned off, including: controlling the connection of a charging switch tube in the bypass on-off control circuit and simultaneously controlling the disconnection of the controllable switch;

when the preset condition is the second preset condition or the fourth preset condition, in step S102, the corresponding bypass on-off control circuit is controlled to be turned on, and the controllable switch is controlled to be turned off, including: controlling the discharge switch tube in the bypass on-off control circuit to be conducted, and simultaneously controlling the controllable switch to be disconnected;

when the preset condition is the first cut-in preset condition, step S102 includes: controlling a charging switch tube in the corresponding main loop on-off control circuit to be conducted; then, the charging switch tube in the corresponding bypass on-off control circuit is controlled to be turned off, and meanwhile, the controllable switch is controlled to be turned off;

when the preset condition is the second cut-in preset condition, step S102 includes: controlling a discharge switch tube in the corresponding main loop on-off control circuit to be conducted; and then controlling a discharge switch tube in the bypass on-off control circuit to be turned off, and simultaneously controlling the controllable switch to be turned off.

Optionally, when the preset condition is the first cut-out preset condition or the third cut-out preset condition, in step S102, after controlling the charge switch tube in the corresponding bypass on-off control circuit to be turned on and simultaneously controlling the controllable switch to be turned off, the method further includes: the charging switch tube in the corresponding main loop on-off control circuit is controlled to be turned off;

when the preset condition is the second cut-out preset condition or the fourth cut-out preset condition, in step S102, after controlling the discharge switch tube in the corresponding bypass on-off control circuit to be turned on and simultaneously controlling the controllable switch to be turned off, the method further includes: and controlling the discharge switch tube in the corresponding main loop on-off control circuit to be turned off.

Optionally, the operation parameters include: voltage, SOC, SOH, or average temperature.

Optionally, step S104 includes: and controlling the controllable switch to be closed.

Optionally, after step S104, the method further includes:

s105, updating parameters of the corresponding battery clusters, and controlling the corresponding power converters to normally operate;

and repeating S101 to S105 until the battery modules in each battery cluster meet the corresponding preset conditions.

Optionally, when there is no inductance in the buffer device, before step S102, the method further includes:

s201, limiting the current on the direct current bus corresponding to the power converter within a preset current range.

Optionally, step S201 includes:

controlling the current on the direct current bus of the corresponding power converter to fall into the preset current range;

and controlling the corresponding power converter to perform wave-sealing operation.

Optionally, a switch box is further disposed between each battery cluster and the corresponding power converter, and when the switch box includes a main loop switch, step S201 includes:

and controlling the corresponding main loop switch to be disconnected.

Optionally, before step S101, the method further includes:

s301, starting up self-checking, and when a self-checking result is normal, controlling a passage between the battery cluster and the corresponding power converter, and controlling the buffer circuit to be in a state of not absorbing voltage peaks;

s302, detecting parameters of the battery cluster, and setting a reference range of operation parameters; and controlling all switches in each battery module to be disconnected;

S303, controlling each battery module to be put into the battery cluster according to an operation mode, and controlling the corresponding power converter to normally operate.

Optionally, the operation mode is: a charge mode or a discharge mode;

the main loop on-off control circuit and the bypass on-off control circuit in the battery module comprise: charging switch tube and discharging switch tube, then:

when the operation mode is the charging mode, controlling each battery module to be put into the battery cluster according to the operation mode, including: controlling the charge switch tube in each main loop on-off control circuit to be conducted;

when the operation mode is the discharge mode, controlling each battery module to be put into the battery cluster according to the operation mode, including: and controlling the discharge switching tube in each main loop on-off control circuit to be conducted.

According to the energy storage system provided by the invention, the control unit can control each battery module to cut in or cut out of the corresponding battery cluster when the corresponding preset condition is met, so that the currently accessed battery module in the battery cluster can be adjusted in real time, and each battery module can meet the corresponding preset condition one by one, namely the same state is achieved, for example, SOC balance is achieved; and at the same time, no energy is wasted. And at least one buffer circuit is arranged in the energy storage system, so that voltage peaks caused by switching in or out any battery module in the corresponding battery cluster can be absorbed, namely energy impact caused by voltage abrupt change is absorbed, and further, the corresponding device is prevented from bearing larger voltage/current stress.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will briefly explain the embodiments or the drawings to be used in the description of the prior art, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.

Fig. 1 and fig. 2 are schematic diagrams of two structures of an energy storage system according to an embodiment of the present invention;

fig. 3 and fig. 4 are schematic views of two other structures of a battery module according to an embodiment of the present invention;

fig. 5 to 8 are four flowcharts of a control method of an energy storage system according to an embodiment of the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.

The invention provides an energy storage system for avoiding energy waste while realizing SOC balance of a battery module.

Referring to fig. 1, the energy storage system includes: a control unit (not shown), at least one battery cluster, at least one buffer circuit 101 and at least one power converter 102; wherein:

the battery cluster comprises a plurality of battery modules (PACK 1, PACK2 and PACK3 … PACKn shown in figure 1) which are connected in series, and two ends of each battery module after being connected in series are used for connecting direct current buses of the corresponding power converter 102; a busbar capacitor C1 is arranged between the anode and the cathode of the direct current busbar.

In practical application, a switch box 103 may be disposed between each battery cluster and the corresponding power converter 102, and the bus capacitor C1 and the main circuit switches S1 and S2 are disposed inside the switch box 103, so as to realize on-off control between the battery cluster and the power converter 102.

It should be noted that the energy storage system may include a plurality of structures as shown in fig. 1, where each power converter 102 may be a DCAC converter, and an ac side grid and/or a load of the DCAC converter; each power converter 102 may be a DCDC converter, and each DCDC converter may be connected to the dc side of the inverter unit of the photovoltaic power generation system, or may be connected to the power grid and/or the load through a DCAC converter provided in the energy storage system.

No matter what structure is adopted, the control unit in the energy storage system can control each battery module to cut in or cut out the corresponding battery cluster when meeting corresponding preset conditions; specifically, in a certain battery cluster, if one battery module meets a preset cutting condition, such as full, empty or abnormal or fault lamp conditions, the control unit controls the battery module to cut out the battery cluster; if the battery modules meet the preset cutting-in condition, for example, all the battery modules are full or all the battery modules are empty, the previously cut-out battery module needs to be cut into the battery cluster again so as to realize the subsequent unified operation, or when the setting parameters of full or empty are changed, or the fault battery module is repaired, or a new battery module needs to be put into operation, the control unit controls the battery module to cut into the battery cluster. That is, the control unit can adjust the battery modules connected to the battery cluster in real time, and only the battery modules which do not meet the corresponding preset conditions remain to be put into the current operation mode, such as the charging mode or the discharging mode, so that each battery module can meet the corresponding preset conditions one by one until all the battery modules in the battery cluster reach the same state, such as the realization of the SOC balance, and the connection adjustment of the battery modules of the battery cluster can be stopped. In addition, the scheme does not need to dissipate the energy of the battery module with more SOC in the form of heat, so that the energy waste is avoided. In addition, in the traditional energy storage system, the battery module adopts active equalization or passive equalization, the equalization current is in the milliamp level, the equalization speed is relatively slow, and the equalization time is relatively constant. However, the energy storage system in this embodiment can increase the equalization speed by 10 times or more through the above-described process.

In practical application, when any battery module in the battery cluster is cut in or cut out, the voltage on the bus capacitor C1 at the dc side of the power converter 102 cannot be suddenly changed, so that a voltage difference of the battery module exists between the voltage of the battery cluster and the voltage on the bus capacitor C1; if the current is directly cut in or cut out, a voltage spike appears on the current path of the battery cluster, so that part of devices on the current path bear larger voltage/current stress, and the safety is affected. Therefore, when the battery module is cut in or cut out from any battery cluster by the control unit, the corresponding buffer circuit 101 is controlled to absorb the voltage spike, so that each device on the current path in the battery cluster is ensured not to bear larger voltage/current stress, and the safety is improved.

Specifically, referring to fig. 1, the buffer circuit 101 includes: and a controllable switch S3 and a buffer device which are connected in parallel. When a battery module is in or out of a corresponding battery cluster, the controllable switch S3 is in an off state, so that the buffer device is put into application and absorbs voltage peaks; when the voltage difference between the voltage of the corresponding battery cluster and the bus capacitor C1 is smaller than a preset difference value, the controllable switch S3 is in a closed state, so that the buffer device is bypassed and stops absorbing the voltage spike.

In practical application, when the voltage of the battery cluster changes, the voltage on the connected dc bus changes rapidly, but the voltage on the bus capacitor C1 cannot be suddenly changed, so the buffer circuit 101 only needs to buffer the voltage difference between the dc bus and the bus capacitor C1; therefore, the buffer circuit 101 may be disposed at any position on the dc bus, such as the dc bus between the battery cluster and the switch box 103 shown in fig. 1, the dc bus between the switch box 103 and the power converter 102, or the dc bus (positive and negative transmission branches) within the switch box 103. Alternatively, the buffer circuit 101 may be connected in series with the bus capacitor C1 between the positive and negative poles of the dc bus, that is, disposed at any end of the bus capacitor C1 between the positive and negative pole transmission branches in the switch box 103. Depending on the specific application environment, it is within the scope of the present application.

As shown in fig. 1, the buffer device specifically includes: a resistor R and an inductor L connected in parallel; due to the existence of the inductor L, when the voltages at two ends of the inductor L are suddenly changed, the corresponding voltage spike can be absorbed; therefore, when the battery module is cut in or out, the corresponding operation does not cause the generation of electric arcs; the corresponding battery cluster can carry out the cut-in or cut-out of the battery module, namely, the current on the direct current bus is kept to be the same as the current in the normal running state, and the cut-in or cut-out operation is carried out on the corresponding battery module. And, when the controllable switch S3 is closed, the resistor R is able to release energy for the inductance L.

In practical application, the buffer device may only include a resistor R, where the resistor R can still absorb a voltage spike when the battery module is cut in or out; however, at this time, if any battery module needs to be cut in or cut out, voltages at two ends of the corresponding switch will be suddenly changed before and after the operation, and an arc is easy to occur; therefore, it is preferable that the current on the dc bus is limited to a predetermined range, such as zero, and then the corresponding battery module is cut in or out to avoid arc generation.

In practical applications, the control unit of the energy storage system may be in any form, such as a BMS (battery management system) shown in fig. 2, where the BMS specifically includes: SMU (system battery management unit), CMU (Cell monitor Unit, battery cluster management unit) of each battery cluster, and BMU (Battery Management Unit ) provided inside each battery module;

the SMU, the CMU and the BMU are in step-by-step communication connection; as shown in fig. 2, each BMU is in communication connection with the CMU in each battery cluster, and the practical application is not limited to this, as long as each BMU can communicate with the corresponding CMU, and each CMU can communicate with the SMU.

The buffer circuit 101 is controlled by the CMU of the corresponding battery cluster. In practice, the main loop switches S1 and S2 in the switch box 103 are also controlled by the CMU of the corresponding battery cluster. In addition, the respective power converters 102 may also be communicatively coupled to CMUs of the same battery cluster. Furthermore, one battery cluster can realize parameter monitoring, battery module on-off control, buffer control, whether to put into operation control, charge-discharge mode control and the like through the CMU. In addition, the CMU and the bus capacitor C1 may be both disposed in the switch box 103 (as shown in fig. 2), and of course, the CMU may alternatively be disposed independently outside the switch box 103, and in addition, in practical application, the bus capacitor C1 may be implemented by a supporting capacitor on the battery side of the power converter 102, which is not necessarily required to be additionally disposed; depending on the specific application environment, it is within the scope of the present application.

In practical application, referring to fig. 1 or 2, each battery module mainly includes: the battery body, the main loop on-off control circuit 201 and the bypass on-off control circuit 202 (only shown in the nth battery module pack because each battery module has the same structure); wherein:

the battery body is connected with the anode and the cathode of the battery module through a main loop on-off control circuit 201, and a bypass on-off control circuit 202 is arranged between the anode and the cathode of the battery module; further, the main loop on-off control circuit 201 and the bypass on-off control circuit 202 may both be controlled by the control unit or the BMU.

Under normal operation, the main loop on-off control circuit 201 is a path, the bypass on-off control circuit 202 is an open circuit, and the corresponding battery body is connected to the corresponding battery cluster. When a certain battery module needs to be cut out, the control unit or the CMU controls the bypass on-off control circuit 202 to be a passage and the main loop on-off control circuit 201 to be an off state through the BMU, and meanwhile, the control unit or the CMU controls the controllable switch S3 in the buffer circuit 101 to be in an off state. When a certain battery module needs to be cut in, the control unit directly or the CMU controls the bypass on-off control circuit 202 to be off and the main loop on-off control circuit 201 to be on again through the BMU, and meanwhile, the control unit or the CMU controls the controllable switch S3 in the buffer circuit 101 to be in an off state.

The main circuit on-off control circuit 201 and the bypass on-off control circuit 202 may each include: a single-path bidirectional switch, as shown in fig. 1 and 3 (only the nth battery module pack is shown as an example in fig. 3, and the other battery modules have the same structure), such as a relay; at this time, the control unit or BMU can realize charging or discharging of the corresponding battery body by controlling the bi-directional switch in the main loop on-off control circuit 201, and can realize charging or discharging bypass of the corresponding battery body by controlling the bi-directional switch in the bypass on-off control circuit 202. However, when any one of the main circuit on-off control circuit 201 and the bypass on-off control circuit 202 is controlled to be switched from the on-off state to the on-off state, the control signal is inevitably delayed, and in practical application, both the control signal and the bypass on-off control circuit are on-off state, so that the corresponding battery body is short-circuited, and the safety of the battery body is threatened; therefore, when the two are on-off controlled, it is necessary to control with dead zone, that is, to control one of them to be switched off and then to control the other to be switched on, which causes the situation that the battery cluster is off and has no current, and therefore, it is not preferable.

Preferably, in practical application, the main circuit on-off control circuit 201 and the bypass on-off control circuit 202 may be both configured to include a two-way unidirectional switch group, that is, the main circuit on-off control circuit 201 and the bypass on-off control circuit 202 may be both configured to include: the battery module comprises a charging switch and a discharging switch, and each battery module is internally provided with a corresponding switch array. At this time, the control unit or the BMU controls the charging switch in the main loop on-off control circuit 201 to charge the corresponding battery body, controls the discharging switch in the main loop on-off control circuit 201 to discharge the corresponding battery body, controls the charging switch in the bypass on-off control circuit 202 to charge the bypass of the corresponding battery body, and controls the discharging switch in the main bypass on-off control circuit 202 to discharge the bypass of the corresponding battery body.

In practical applications, a charge switch and a discharge switch may be configured in anti-parallel, as shown in fig. 2, and the charge switch includes: a charge switching tube (K1-1, K1-2, K1-3 … K1-n as shown in fig. 2) and a charge diode, the discharge switch comprising: discharge switching tubes (K4-1, K4-2, K4-3 … K4-n as shown in FIG. 2) and discharge diodes; within the bypass on-off control circuit 202, the charge switch includes: a charge switching tube (K2-1, K2-2, K2-3 … K2-n as shown in fig. 2) and a charge diode, the discharge switch comprising: a discharge switching tube (K3-1, K3-2, K3-3 … K3-n as shown in FIG. 2) and a discharge diode; each diode is connected in reverse series with the body diode in the corresponding switching tube.

Alternatively, the charging switch and the discharging switch may be arranged in reverse series, as shown in fig. 4 (only the nth battery module pack is shown in fig. 4 as an example, and the structures in other battery modules are the same), where the charging switch includes a charging switch tube, the discharging switch includes a discharging switch tube, and the charging switch tube and the discharging switch tube are both provided with body diodes, which are in reverse series; and the body diode in the discharging switch tube and the charging switch tube form a branch circuit in the charging direction of the battery cluster, and the body diode in the charging switch tube and the discharging switch tube form a branch circuit in the discharging direction of the battery cluster.

In either of the modes shown in fig. 2 and fig. 4, when one of the switching tubes in any one of the control circuits is closed, the diode connected in series with the same switching tube as shown in fig. 2 or the body diode of the other switching tube as shown in fig. 4 will automatically realize reverse cut-off, thereby avoiding short circuit to the corresponding battery body; therefore, it is not necessary to control another control circuit to switch to the open circuit, and no dead zone switching can be realized.

The invention also provides a control method of the energy storage system, which is applied to the control unit in the energy storage system according to any embodiment; the specific structure and principle of the energy storage system can be referred to the above embodiments, and will not be described in detail.

As shown in fig. 5, the control method includes:

s101, judging whether each battery module in the corresponding battery cluster of the energy storage system meets corresponding preset conditions.

The preset condition may be a cut-out preset condition or a cut-in preset condition; for example, when a certain battery module in the same battery cluster is full, or is empty, or has a fault, or needs to be replaced with a new battery module, etc., the cutting preset condition is satisfied; when the setting parameters of full or empty are changed, or the fault battery module is repaired, or a new battery module needs to be put into operation, the cut-in preset condition is met; or when the battery cluster needs to adjust the operation mode, for example, from the charging mode to the discharging mode, or from the discharging mode to the charging mode, all the battery modules can be adjusted to be in the same state, and the battery clusters can be considered to meet the cut-in preset condition; depending on the specific application environment, it is within the scope of the present application.

If any battery module meets the corresponding preset condition, step S102 is executed.

S102, controlling the corresponding battery module to cut in or cut out of the battery cluster; meanwhile, the corresponding buffer circuit in the energy storage system is controlled to absorb voltage peaks caused by switching in or out of the corresponding battery module.

For the situation of a single-path bidirectional switch, when a certain battery module is cut out, the bidirectional switch in the main loop on-off control circuit needs to be controlled to be turned off, and meanwhile, the controllable switch in the buffer circuit is controlled to be turned off to absorb voltage spikes; and then controlling the two-way switch in the bypass on-off control circuit to be conducted. When a certain battery module is cut in, the bidirectional switch in the bypass on-off control circuit is required to be controlled to be disconnected firstly, and meanwhile, the controllable switch is controlled to be disconnected to absorb voltage spikes; and then controlling the two-way switch in the main loop on-off control circuit to be conducted. That is, on-off control with dead zones is required to avoid short-circuiting to the battery body.

For the situation of a two-way unidirectional switch group, when a certain battery module is cut out, the bypass on-off control circuit can be controlled to be conducted firstly, and meanwhile, the controllable switch is controlled to be disconnected to absorb voltage spikes; the main loop on-off control circuit can be controlled to be turned off again. When a certain battery module is cut in, the on-off control circuit of the main loop can be controlled to be conducted firstly; and then the bypass on-off control circuit is controlled to be turned off, and meanwhile, the controllable switch is controlled to be turned off to absorb voltage spikes. That is, the short circuit to the battery body is avoided by the reverse cut-off function of the charge switch and the discharge switch thereof, and thus, control can be achieved without dead zones, and any cut-in or cut-out operation does not cause the cut-out of the battery cluster.

S103, judging whether the voltage difference between the battery cluster and the corresponding bus capacitor is in a preset voltage range.

If the voltage difference is not within the preset voltage range, the absorption of the voltage spike by the buffer circuit is continued. If the voltage difference is within the preset voltage range, step S104 is performed.

S104, controlling the buffer circuit to stop absorbing the voltage spike.

When the voltage difference between two ends of the buffer device in the buffer circuit, such as the voltage difference between two ends of the inductor L in fig. 2, is within the preset voltage range, the controllable switch can be controlled to be closed, the buffer device is bypassed, the inductor L in fig. 2 is prevented from continuously consuming energy, and the energy in the inductor L is released through the resistor R.

In a specific embodiment, the preset condition may be any one of the following: when the battery cluster is charged, the operation parameters of the corresponding battery modules reach the first cut-out preset condition of the preset upper limit value; when the battery cluster discharges, a second cutting-out preset condition that the operation parameter of the corresponding battery module reaches a preset lower limit value is achieved; when the battery cluster is charged, a third cutting-out preset condition is met when the corresponding battery module is abnormal or fails; when the battery cluster discharges, a fourth cutting-out preset condition is generated when the corresponding battery module is abnormal or fails; a first cut-in preset condition requiring recovery from the charge bypass state to the charge state; a second cut-in preset condition is required to restore from the discharge bypass state to the discharge state. Wherein the operating parameters may be: the voltage, SOC, SOH (state of health) or average temperature are not particularly limited herein, and may be any one depending on the application environment, and are within the scope of the present application.

Taking the case that the main loop on-off control circuit and the bypass on-off control circuit in the battery module all comprise two-way unidirectional switch groups, at this time: if the preset condition is the first cut preset condition or the third cut preset condition, step S102 includes: the charging switch tube in the corresponding bypass on-off control circuit is controlled to be conducted, and meanwhile the controllable switch is controlled to be disconnected; and then, the charging switch tube in the corresponding main loop on-off control circuit can be controlled to be turned off. If the preset condition is the second cut preset condition or the fourth cut preset condition, step S102 includes: the discharge switch tube in the corresponding bypass on-off control circuit is controlled to be conducted, and meanwhile the controllable switch is controlled to be disconnected; then, the discharge switch tube in the corresponding main loop on-off control circuit can be controlled to be turned off. If the preset condition is the first entering preset condition, step S102 includes: controlling the charge switch tube in the corresponding main loop on-off control circuit to be conducted; and then the charging switch tube in the corresponding bypass on-off control circuit is controlled to be turned off, and the controllable switch is controlled to be turned off. If the preset condition is the second hand-in preset condition, step S102 includes: controlling the connection of a discharge switch tube in a corresponding main loop on-off control circuit; and then the discharge switch tube in the corresponding bypass on-off control circuit is controlled to be turned off, and the controllable switch is controlled to be turned off.

By adopting the control method provided by the embodiment, when the battery module is cut out or cut in, the switching of the switch arrays in the corresponding battery module and the input of the buffer circuit are reasonably controlled, so that the possible switch voltage/current peak on the main switch device can be effectively restrained, and the energy impact caused by voltage mutation is absorbed.

In addition, when a certain battery module is full, empty, failed or supplemented, the main power circuit of the battery cluster can be cut out or cut in by the current of the module without dead zone through the cut-out/cut-in operation of the switch array and the input of the buffer circuit. And in addition, when the energy storage system is charged/discharged, the action of cutting off the battery module possibly occurs, and a main loop switch in the switch box is not required to be cut off, so that no dead zone switching is realized.

Preferably, as shown in fig. 6, the control method further includes, after step S104:

and S105, updating parameters of the corresponding battery clusters, and controlling the corresponding power converters to operate normally.

For example, in a charge-discharge scene, one battery module is cut out every time, the number of connected battery modules in a battery cluster, the voltage of the battery modules, the system voltage and the like can be updated, so that charge-discharge and one-by-one cutting out of other battery modules can be continued. When the SOC of each battery module is consistent, if a shutdown instruction is received, the battery system can be shut down and stop running. Other conditions are similar and will not be described in detail.

In addition, as shown in fig. 7, the control method may further include, before step S101:

s301, starting up self-checking, and when the self-checking result is normal, controlling a path between the battery cluster and the corresponding power converter, and controlling the buffer circuit to be in a state of not absorbing voltage peaks.

S302, detecting parameters of a battery cluster, and setting a reference range of operation parameters; and controls all switches in each battery module to be turned off.

S303, controlling each battery module to be put into the battery cluster according to the operation mode, and controlling the corresponding power converter to normally operate.

The operation mode is as follows: a charge mode or a discharge mode. If the operation mode is a charging mode, each battery module is controlled to be put into the battery cluster according to the operation mode, specifically: and controlling the charge switch tube in each main loop on-off control circuit to be conducted. And if the operation mode is a discharge mode, controlling each battery module to be put into the battery cluster according to the operation mode, specifically: and controlling the discharge switch tubes in the on-off control circuits of the main loops to be conducted.

It should be noted that, when the control unit is specifically a BMS, the control method may be specifically implemented by any level of management unit, and the following specifically describes, by taking a CMU as an example, the control method being executed in conjunction with the structure shown in fig. 2:

The system is started and self-checking is carried out on the system through the CMU and the BMU: detecting the access number n of the battery modules, the battery module voltages (such as Vmod_1, vmod_2, vmod_3 … Vmod_n and the system voltage Vsys shown in the figure), and opening all switching tubes (such as K1-n, K2-n, K3-n and K4-n in PACKn) in all the battery modules; the SOC state of the battery module can be known from the battery module voltage vmod_n. When the state of each battery module is normal, the CMU closes the main loop switches S1, S2 and the controllable switch S3.

If the operation mode is the charging mode, the CMU issues a startup command to control the charging switch tubes (e.g., K1-n in pack) in each BMU closed main loop on-off control circuit 201, and the other switch tubes are turned off. If the operation mode is a discharging mode, the CMU issues a start command to control the discharging switch tubes (e.g., K4-n in pack) in each BMU closed main loop on-off control circuit 201, and the other switch tubes are turned off.

The CMU then obtains SOC information for each battery module based on the ocv_soc calibration, and issues a charge or discharge limiting current Icn to the power converter 102.

(1) In the normal charging process, along with the rise of the voltage of the battery module, when the mth battery module PACKm reaches the preset upper limit value Vmod max or the set high SOC threshold value at first, the voltage of other battery modules is smaller than the preset upper limit value Vmod max, and at the moment, the mth battery module PACKm needs to be bypassed, namely the operation of cutting out a main power loop is performed, and the rest of modules which are not full of electricity are continuously charged.

In the charging process, the cut-out control logic of the mth battery module pack is as follows: k2 closed and S3 open→after RL absorption→s3 closed.

Specifically, through the BMU of the mth battery module PACKm, the charging switch tube K2-m in the bypass on-off control circuit 202 is controlled to be closed, and meanwhile, the CMU controls the controllable switch S3 in the buffer circuit 101 to be opened, so that a buffer device is connected into a main loop, and the inductance L is used for absorbing energy impact generated when the K2-m is closed, so that current impact cannot be generated after voltage mutation. At this time, the charging switch tubes K1-m in the main circuit on-off control circuit 201 may be turned off or not turned off, and if the control of K1-m is turned off, the control of K1-m is required to be turned off after K2-m is turned on, so as to avoid the occurrence of open circuit of the battery cluster. After the buffer circuit acts, when the voltage difference between the front and rear of the inductor L, namely the voltage difference between the voltage Ub of the battery cluster and the voltage Uc on the bus capacitor C1 is smaller than a certain threshold value, the controllable switch S3 is closed again, the buffer device is bypassed, and the main power loop of the battery module is cut out.

After the cut-out is completed, the power converter 102 continues to charge the remaining n-1 battery modules. And the CMU updates parameters such as the access number n of the modules, the voltage of the battery modules and the like, and continuously charges the rest battery modules through the power converter 102, and the same control logic is performed until all the battery modules reach a preset upper limit value Vmod max or a set SOC high threshold value.

(2) In the normal charging process, after some battery modules are cut out by the bypass, in the subsequent working engineering, when the battery modules need to be cut into the system, the state of the internal switch array of the bypassed battery modules pack can be known as follows: k2-m is closed, and K1-m, K3-m and K4-m are all in open states. Assuming that the battery module pack needs to be cut into the system, in the charging process, the cut-in control logic of the battery module is as follows: k1 closed→k2 open and S3 open→after RL absorption→s3 closed.

Specifically, through the BMU of battery module PACKm, control K1-m to close earlier, then control K2-m and open, and CMU simultaneously control controllable switch S3 disconnection, with buffer device access major loop, absorb the energy impact that K2-m produced when opening with inductance L, can not produce the electric current impact by difference after making voltage abrupt change. After the buffer circuit acts, when the voltage difference between the front and the rear of the inductor L, namely the voltage difference between Ub and Uc is smaller than a certain threshold value, the controllable switch S3 and the bypass buffer device are closed again, and the battery module is cut into the main power loop.

After the cut-in is completed, the CMU updates parameters such as the number of access modules n, the battery module voltage, etc., and the power converter 102 continues to charge all the battery modules, so that the same control logic can recover all the bypassed battery modules in the system.

(3) In the normal discharging process, along with the reduction of the voltage of the battery module, when the mth battery module PACKm reaches the preset lower limit value Vmod min or the set SOC low threshold value at first, the voltages of other battery modules are all larger than the preset lower limit value Vmod min, and at the moment, the mth battery module PACKm needs to be bypassed, namely the operation of cutting out a main power loop is performed, and the rest of unreleased modules continue to be discharged.

In the discharging process, the module cut-out control logic of the mth battery module pack is as follows: k3 closed and S3 open→K4 open→RL absorb followed by S3 closed.

Specifically, through the BMU of battery module PACKm, control K3-m to close first, and CMU control controllable switch S3 opens simultaneously, inserts the main loop with the buffer device, then opens K4-m, absorbs the energy impact that K3-m produced when closing with inductance L, makes the voltage can not produce the current impact after the abrupt change. After the buffer circuit acts, when the voltage difference between the front and the rear of the inductor L, namely the voltage difference between Ub and Uc is smaller than a certain threshold value, the controllable switch S3 and the bypass buffer device are closed again, and the battery module cuts out the main power loop.

After the cut-out is completed, the power converter 102 continues to discharge the remaining n-1 battery modules. And the CMU updates parameters such as the access number n of the modules, the voltage of the battery modules and the like, and continuously discharges the rest batteries through the power converter 102, and the same control logic is performed until all the battery modules reach a preset lower limit value Vmod min or a set SOC low threshold value.

(4) In the normal discharging process, after some modules are cut out by the bypass, in the subsequent working engineering, when the battery module needs to be cut into the system, the state of the switch array of the bypassed battery module pack is as follows: k3-m is closed, and K1-m, K2-m and K4-m are all in open states. Assuming that the battery module pack needs to be cut into the system, in the discharging process, the cut-in control logic of the battery module is as follows: k4 closed→k3 open and S3 open→after RL absorption→s3 closed.

Specifically, through the BMU of battery module PACKm, control K4-m to close earlier, then control K3-m and open, the CMU control controllable switch S3 opens simultaneously, inserts the main loop with buffer device, absorbs the energy impact that K3-m produced when opening with inductance L, makes the voltage can not produce the current impact after abrupt change. After the buffer circuit acts, when the voltage difference between the front and the rear of the inductor L, namely the voltage difference between Ub and Uc is smaller than a certain threshold value, the controllable switch S3 and the bypass buffer device are closed again, and the battery module is cut into the main power loop.

After the cut-in is completed, the CMU updates parameters such as the number of connected modules n, the battery module voltage, etc., and continues to discharge all the battery modules through the power converter 102, so that the same control logic can recover all the bypassed battery modules in the system.

(5) The fault module cuts out the control logic: when the system judges that one battery module is abnormal or fails and needs to be cut out, the cutting-out operation of the battery module is executed.

The cut-out control logic of the m-th battery module PACKm is the same as the cut-out logic during charging and discharging, namely, when the module is abnormal or has faults, the cut-out control logic of the corresponding execution module is judged to be in a charging or discharging state during the main power loop.

As can be seen from the above description, under the configuration shown in fig. 2, the main loop switch in the switch box is not required to be turned off, when a certain battery module is full/empty/failed or is supplemented, the main power loop of the battery cluster can be cut/cut through the switch array of the battery module, and the buffer circuit is combined, so that the battery module can be quickly cut or cut into the main power loop, and the cut/cut-in of the battery module with current and without dead zone can be realized in the charging/discharging process of the system.

In addition, in the application of the energy storage system, the SOC calculation of the battery module is the basis of system control; in this embodiment, a centralized or decentralized SOC state estimation scheme is used to calculate the SOC of each battery module individually. Each battery module can be independently controlled according to the SOC state of the battery module, and the problem that all modules are forcedly calibrated to be consistent in SOC after one module is full or empty in the traditional algorithm is solved.

In addition, due to different manufacturers, the traditional battery modules have the problems of consistency of production batches and battery cores, and the like, when the system capacity expansion or module replacement is performed, complicated power supplementing operation is required, so that the SOC of the battery module to be replaced is consistent with the system SOC, then the battery module is replaced, the operation and maintenance process is complicated, and the problem of barrel effect of the new and old battery modules cannot be solved. The control method provided by the embodiment independently controls each battery module, solves the problems of capacity expansion or replacement and power supply operation, and can realize the instant replacement and instant use of the battery module.

It should be noted that, as described in the above embodiment, when the inductance L exists in the buffer device, the battery module may be loaded to perform the on-off operation; when the buffer device has no inductance L, if the battery module is still loaded to perform the corresponding operation, the corresponding switch may possibly generate an arc during the operation, and there is a risk of arc discharge, so the control method may further include, based on the above embodiment, as shown in fig. 8 (shown on the basis of fig. 5 as an example), that is, before step S102:

s201, the CMU limits the current on the direct current bus of the corresponding power converter to a preset current range.

The step S201 specifically includes:

(1) The CMU controls the current on the dc bus of the corresponding power converter to drop to within a preset current range.

(2) The CMU controls the corresponding power converter to perform wave-sealing operation; alternatively, the CMU may directly control the opening of the corresponding main loop switch. Depending on the specific application environment, it is within the scope of the present application.

In this specification, each embodiment is described in a progressive manner, and identical and similar parts of each embodiment are all referred to each other, and each embodiment mainly describes differences from other embodiments. In particular, for a system or system embodiment, since it is substantially similar to a method embodiment, the description is relatively simple, with reference to the description of the method embodiment being made in part. The systems and system embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The features described in the various embodiments of the present disclosure may be interchanged or combined with one another in the description of the disclosed embodiments to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An energy storage system, comprising: the power converter comprises a control unit, at least one battery cluster, at least one buffer circuit and at least one power converter; wherein:

the buffer circuit is controlled by the control unit and is used for absorbing voltage peaks caused by switching in or out any battery module in the corresponding battery cluster, so that a main loop switch in the switch box is not required to be disconnected.

2. The energy storage system of claim 1, wherein the buffer circuit comprises: a controllable switch and a buffer device connected in parallel;

3. The energy storage system of claim 2, wherein the buffer device comprises: resistance, or resistance and inductance connected in parallel.

4. The energy storage system of claim 1, wherein the buffer circuit is disposed on the dc bus or the buffer circuit and the bus capacitor are connected in series between the positive and negative poles of the dc bus.

5. The energy storage system of any of claims 1-4, wherein the battery module comprises: the battery comprises a battery body, a main loop on-off control circuit and a bypass on-off control circuit; wherein:

6. The energy storage system of claim 5, wherein said main loop on-off control circuit and said bypass on-off control circuit each comprise: a two-way unidirectional switch group; the two-way unidirectional switch group comprises: a charge switch and a discharge switch; the control unit controls the charging switch in the main loop on-off control circuit to charge the corresponding battery body, controls the discharging switch in the main loop on-off control circuit to discharge the corresponding battery body, controls the charging switch in the bypass on-off control circuit to realize a charging bypass for the corresponding battery body, and controls the discharging switch in the bypass on-off control circuit to realize a discharging bypass for the corresponding battery body;

Or,

7. The energy storage system of claim 6, wherein the charge switch comprises: a charging switch tube and a charging diode which is reversely connected with the body diode in the charging switch tube in series; the discharge switch includes: a discharge switch tube and a discharge diode which is reversely connected with the body diode in the discharge switch tube in series; the charging switch is reversely connected in parallel with the discharging switch;

or,

8. The energy storage system of claim 5, wherein a switch box is further disposed between each of the battery clusters and the corresponding power converter, and the switch box comprises: and a main loop switch.

9. The energy storage system of any of claims 1-4, wherein the control unit is a battery management system, BMS, and the BMS comprises: the system comprises a system battery management unit SMU, battery cluster management units CMU of each battery cluster and battery management units BMU arranged in each battery module;

the SMU, the CMU and the BMU are in step-by-step communication connection;

the CMU is communicatively coupled to the power converter.

10. The energy storage system of any of claims 1-4, wherein the power converter is a DCAC converter; or,

11. A control method of an energy storage system, characterized by being applied to a control unit in an energy storage system according to any one of claims 1-10; the control method comprises the following steps:

s104, controlling the buffer circuit to stop absorbing the voltage spike.

12. The method of claim 11, wherein the preset condition is a cut-out preset condition or a cut-in preset condition; the buffer circuit includes: a controllable switch and a buffer device connected in parallel; and in the main loop on-off control circuit and the bypass on-off control circuit in the battery module, all include: a single-path bi-directional switch; then:

13. The method of claim 11, wherein the preset condition is a cut-out preset condition or a cut-in preset condition; the buffer circuit includes: a controllable switch and a buffer device connected in parallel; the main loop on-off control circuit and the bypass on-off control circuit in the battery module comprise two-way unidirectional switch groups; then:

14. The method according to claim 13, wherein when the preset condition is the cut-out preset condition, in step S102, after controlling the corresponding bypass on-off control circuit to be turned on and simultaneously controlling the controllable switch to be turned off, the method further comprises: and controlling the on-off control circuit of the corresponding main loop to be turned off.

15. The method of claim 13, wherein the cut-out preset condition is any one of:

the cutting preset condition is any one of the following conditions:

16. The method of claim 15, wherein the main loop on-off control circuit and the bypass on-off control circuit in the battery module each comprise: charging switch tube and discharging switch tube, then:

17. The method according to claim 16, wherein when the preset condition is the first cut-out preset condition or the third cut-out preset condition, in step S102, after controlling the charge switch tube in the bypass on-off control circuit to be turned on and simultaneously controlling the controllable switch to be turned off, the method further comprises: the charging switch tube in the corresponding main loop on-off control circuit is controlled to be turned off;

18. A method of controlling an energy storage system according to any one of claims 15 to 17, wherein the operating parameters include: voltage, remaining charge SOC, battery health SOH, or average temperature.

19. The method of any one of claims 13-14, 16-17, wherein step S104 includes: and controlling the controllable switch to be closed.

20. The method of any one of claims 11-17, further comprising, after step S104:

21. The method according to any one of claims 11-17, further comprising, when there is no inductance in the buffer device, prior to step S102:

22. The method of claim 21, wherein step S201 includes:

23. The method according to claim 21, wherein a switch box is further disposed between each of the battery clusters and the corresponding power converter, and when the switch box includes a main loop switch, step S201 includes:

and controlling the corresponding main loop switch to be disconnected.

24. The method of any one of claims 11-17, further comprising, prior to step S101:

25. The method of claim 24, wherein the operating mode is: a charge mode or a discharge mode;