CN113325321B - Energy storage system floating state battery power failure detection method and energy storage system - Google Patents
Energy storage system floating state battery power failure detection method and energy storage system Download PDFInfo
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- CN113325321B CN113325321B CN202110750625.XA CN202110750625A CN113325321B CN 113325321 B CN113325321 B CN 113325321B CN 202110750625 A CN202110750625 A CN 202110750625A CN 113325321 B CN113325321 B CN 113325321B
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- 238000004146 energy storage Methods 0.000 title claims abstract description 138
- 238000007667 floating Methods 0.000 title claims abstract description 68
- 238000001514 detection method Methods 0.000 title claims description 5
- 238000000034 method Methods 0.000 claims abstract description 46
- 238000007599 discharging Methods 0.000 claims description 21
- 238000005070 sampling Methods 0.000 abstract description 4
- 239000003990 capacitor Substances 0.000 description 10
- 230000008569 process Effects 0.000 description 9
- 238000005265 energy consumption Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 230000008713 feedback mechanism Effects 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000004891 communication Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000002457 bidirectional effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000284 extract Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/54—Testing for continuity
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for AC mains or AC distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
- H02J7/0036—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using connection detecting circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0047—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with monitoring or indicating devices or circuits
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
- Secondary Cells (AREA)
Abstract
The invention provides a method for detecting power failure of a floating state battery of an energy storage system and the energy storage system, which are applied to the energy storage system comprising an energy storage converter PCS, wherein the method comprises the following steps: after the energy storage system enters a floating charge state, acquiring a PCS direct-current side bus reference voltage of the energy storage converter; switching a reference current instruction of the current loop into a preset discharge current instruction; after a first preset time, the current direct-current side bus voltage is obtained, and whether the battery side has a power failure or not is judged according to the direct-current side bus voltage and the direct-current side bus reference voltage. Therefore, the battery power failure can be judged without increasing battery sampling data, and the DC side power is disturbed to carry out low-power discharge in a pulse form, so that the floating charge operation of the system is not influenced.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a method for detecting power failure of a battery in a floating state of an energy storage system and the energy storage system.
Background
The battery energy storage system is a key technology of photovoltaic power generation and the like, but the battery side of the energy storage system needs to be charged and discharged to execute related functions, so once the battery side is powered down and disconnected, the loss which is difficult to compensate is easily caused to the whole energy storage system.
In the prior art, the power failure of a battery is generally judged by detecting the voltages at two ends of a direct current side; however, in the energy storage system, the direct-current side voltage is acted by the voltages at the two ends of the battery and the voltage ring of the energy storage system, so that even if the battery side in the floating state is disconnected, the direct-current side voltage connected with the battery side is still the same as the floating state in characteristics, and whether the battery in the energy storage system fails to power down or not cannot be judged.
Disclosure of Invention
The invention solves the problem that the direct-current side voltage in a floating charge state cannot distinguish whether the battery side is disconnected or not in characteristics.
In order to solve the above problems, the present invention provides a method for detecting power failure of a floating state battery of an energy storage system, which is applied to an energy storage system including an energy storage converter PCS, and includes:
After the energy storage system enters a floating charge state, acquiring a PCS direct-current side bus reference voltage of the energy storage converter;
switching a reference current instruction of the current loop into a preset discharge current instruction;
after a first preset time, the current direct-current side bus voltage is obtained, and whether the battery side has a power failure or not is judged according to the direct-current side bus voltage and the direct-current side bus reference voltage.
Therefore, the external characteristics of the two conditions of disconnection of the battery side and disconnection of the battery side are obviously distinguished by switching the charging current instruction into the discharging current instruction, so that the power failure of the battery side is judged through the voltage of the direct current side, and the method is simple and convenient and has high accuracy; on the one hand, the method can be realized directly through the existing signal acquisition without acquiring a new type of electric signal; on the other hand, the actual electric energy consumption of the battery side is low, and the battery side is prevented from falling out of a floating state.
Optionally, the method further comprises: and after a second preset time, switching the discharge current command back to the reference current command of the current loop.
Optionally, after the energy storage system enters the floating state, before the reference voltage of the PCS direct-current side bus of the energy storage converter is obtained, the method further includes:
Acquiring current dispatching power and current power, battery side voltage and charging upper limit voltage of an energy storage system, and judging whether the energy storage system enters a floating charge state according to the current dispatching power, the current power, the battery side voltage and the charging upper limit voltage;
optionally, the specified current value in the discharge current command is less than 40% of the PCS rated current of the energy storage converter.
Optionally, the specified current value in the discharge current instruction is within 10% -20% of the rated current of the PCS of the energy storage converter.
Optionally, after all the following conditions are satisfied, determining that the energy storage system enters a floating state:
Condition one, the current power is less than 5% of the current scheduling power;
And in a second condition, the difference between the charging upper limit voltage and the battery side voltage is less than 5V.
Optionally, the second preset time is longer than the dc under-voltage protection time.
Optionally, the method further comprises: and after the power failure fault occurs at the battery side, controlling the PCS of the energy storage converter to stop running.
Optionally, after the first preset time, acquiring a current dc side bus voltage, and judging whether a power failure occurs on the battery side according to the dc side bus voltage and the dc side bus reference voltage, including:
after a first preset time, acquiring the current direct-current side bus voltage;
calculating the battery side power-down speed according to the first preset time, the direct-current side bus voltage and the direct-current side bus reference voltage;
If the power-down speed of the battery side is greater than a preset power-down speed threshold, judging that the power-down fault occurs on the battery side;
and if the power-down speed of the battery side is smaller than the power-down speed threshold, judging that the power-down fault of the battery side does not occur.
Next, the present invention provides an energy storage system comprising: an energy storage converter PCS and a storage battery;
One end of the PCS of the energy storage converter is connected with the output end of the storage battery, and the other end of the PCS of the energy storage converter is electrically connected with three phases of an alternating current power grid;
The PCS is provided with a PCS controller, and the PCS controller is in communication connection with the storage battery and is used for executing the method for detecting the power failure of the floating state battery of the energy storage system.
Therefore, the battery power failure can be judged without increasing battery sampling data, and the DC side power is disturbed to carry out low-power discharge in a pulse form, so that the floating charge operation of the system is not influenced.
Drawings
FIG. 1 is a schematic flow chart of a method for detecting power failure of a floating-charge battery of an energy storage system according to an embodiment of the invention;
FIG. 2 is a flowchart illustrating a method for detecting a power failure of a floating battery of an energy storage system according to another embodiment of the present invention;
FIG. 3 is a flowchart illustrating a method for detecting a power failure of a floating battery of an energy storage system according to another embodiment of the present invention;
FIG. 4 is a flowchart illustrating a method for detecting a power failure of a floating battery of an energy storage system according to another embodiment of the present invention;
fig. 5 is a flowchart illustrating a method S400 for detecting a power failure of a floating-state battery of an energy storage system according to an embodiment of the invention;
FIG. 6 is a schematic diagram illustrating a method for detecting a power failure of a floating battery of an energy storage system according to an embodiment of the present invention;
fig. 7 is a schematic diagram of an energy storage system according to an embodiment of the invention.
Reference numerals illustrate:
10-an energy storage converter PCS; 11-a main power loop; a 12-PCS controller; 20-direct current side; 21-bus capacitance; 22-accumulator.
Detailed Description
The energy storage system generally comprises an energy storage converter PCS, one end of the energy storage converter PCS is communicated with an alternating current power grid, and the other end of the energy storage converter PCS is communicated with a direct current side which generally comprises a storage battery and a bus capacitor for stabilizing voltage and the like. In the working process of the energy storage system, control instructions of the current loop and the voltage loop are received, and the main power loop is regulated according to the control instructions, so that the charging and discharging processes of the storage battery are completed, energy conversion is carried out, and the energy storage system can directly supply power for an alternating current load under the condition of no power grid.
If the battery side is to be charged, a charging instruction including an upper charging limit is received, wherein the upper charging limit is that the battery side is charged to be the same as or close to the upper charging limit; in fact, when the battery side is charged, if the battery side is in a nearly full state, a float state is entered, and in this state, the battery side is charged with a very small current. In this case, the reference voltage given by the voltage loop is very close to the dc side voltage, so that the actual power of the energy storage converter PCS is limited (in this state the actual power of the PCS is much smaller than the theoretical scheduled power), in which case, even if the battery side is in the off state, the PCS still remains in a similar operating state, so that it is impossible to distinguish from the current operating state whether the battery side is off.
For convenience of distinguishing, in the application, the whole part of the battery side and the bus capacitor is regarded as a direct current side, so that more accurate distinguishing is made.
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein.
Fig. 1 is a schematic flow chart of a method for detecting power failure of a floating battery of an energy storage system according to an embodiment of the application. The application discloses a method for detecting power failure of a floating state battery of an energy storage system, which is applied to the energy storage system comprising an energy storage converter PCS, and comprises the following steps:
s200, after the energy storage system enters a floating charge state, acquiring a PCS direct-current side bus reference voltage of the energy storage converter;
the PCS of the energy storage converter can control the charging and discharging processes of the storage battery to perform alternating current-direct current conversion, and can directly supply power for an alternating current load under the condition of no power grid. The PCS is composed of a DC/AC bidirectional converter, a controller and the like. The PCS controller/the energy storage converter PCS receives the control command through communication, and controls the energy storage converter to charge or discharge the battery according to the sign and the size of the power command, so that the active power of the power grid is regulated.
After the energy storage system enters a floating state, the busbar voltage at the PCS direct current side of the energy storage converter can remain unchanged (fluctuation can be generated in the floating state, but the fluctuation is small). In this case, the bus voltage on the dc side of the energy storage converter PCS is detected, and the bus voltage is used as the bus reference voltage on the dc side of the energy storage converter PCS.
S300, switching a reference current instruction of a current loop into a preset discharge current instruction;
in a floating state, the reference current instruction of the current loop is a charging current instruction, and the charging current instruction is determined by the output of the voltage loop; under a charging current instruction, the PCS of the energy storage converter converts alternating current of the alternating current power grid into direct current to charge a storage battery at the direct current side.
After the reference current command is switched to the discharge current command, the storage battery on the direct current side is discharged by the PCS under the discharge current command.
The preset discharging current command may be pre-stored in the energy storage converter PCS or may be pre-stored in other components.
Optionally, the specified current value in the discharge current command is less than 40% of the PCS rated current of the energy storage converter.
The PCS itself has rated power, rated voltage and rated current; the specified current value in the discharging current instruction is set to be smaller than 40% of the rated current of the PCS of the energy storage converter, so that excessive electric energy loss of the battery side during discharging can be avoided by setting the discharging instruction with a small current value, and the floating charge state can be exited.
Optionally, the specified current value in the discharge current instruction is within 10% -20% of the rated current of the PCS of the energy storage converter. In this way, on one hand, the battery side can be prevented from losing excessive electric energy during discharging, so that the floating state is exited; on the other hand, when the battery side is disconnected, the current of the dc side discharge is too small to be easily found or determined as disconnected.
S400, after a first preset time, acquiring the current direct-current side bus voltage, and judging whether a power failure fault occurs on the battery side according to the direct-current side bus voltage and the direct-current side bus reference voltage.
The execution of the discharge current command is not completed in a moment, and the discharge current command can be fully executed by setting the first preset time.
Optionally, the first preset time is greater than 1s. In this way, the discharge current execution can be executed, and the discharge process appears on the external characteristics of the energy storage system, so that the observation and judgment are convenient.
When the energy storage system is in a floating charge state, the charging current instruction has no great influence on the voltages of the battery side and the direct current side, and is changed into a discharging current instruction at the moment, if the battery side does not generate a power failure, the discharging process can be outwards shown, but the actual electric energy consumption of the battery side is less, so that the change of the voltages of the battery side and the direct current side is small for the whole battery side, and the direct current side cannot directly exit the floating charge state; if the battery side fails, the direct current side voltage is directly determined by the capacitor and the voltage loop, and even if the discharging current command is small, the electric energy in the capacitor is rapidly consumed, and the direct current side voltage is rapidly reduced.
Therefore, the external characteristics of the two conditions of disconnection of the battery side and disconnection of the battery side are obviously distinguished by switching the charging current instruction into the discharging current instruction, so that the power failure of the battery side is judged through the voltage of the direct current side, and the method is simple and convenient and has high accuracy; on the one hand, the method can be realized directly through the existing signal acquisition without acquiring a new type of electric signal; on the other hand, the actual electric energy consumption of the battery side is low, and the battery side is prevented from falling out of a floating state.
In the application, the power failure fault refers to a fault that the battery side is disconnected.
Optionally, as shown in fig. 2, the method for detecting power failure of the floating state battery of the energy storage system further includes:
S500, after a second preset time, switching the discharge current command back to the reference current command of the current loop.
If it is determined in step S400 that the power failure has not occurred on the battery side, step S500 may be directly executed, and if it is determined in step S400 that the power failure has occurred on the battery side, other measures may be taken or the step may be directly executed, or other power failure measures may be taken while the step is executed.
It should be noted that, the reference current command of the current loop is determined by the feedback mechanism of the current loop itself, and in this step, the reference current command of the current loop refers to the reference current command determined by the feedback mechanism of the current loop itself at the present moment, which is the same as the reference current command of the current loop in step S300, but the representative specific current command is not necessarily the same in size, because it represents the reference current command of the current loop at a different moment.
The feedback mechanism of the current loop does not disappear, but only after the current loop is switched to the discharge current instruction, the feedback of the current loop is recorded only, and the charge current instruction of the current loop is not continuously executed until the discharge current instruction is switched.
In this way, the step is combined with the previous step, after the energy storage system enters a floating charge state, the charging current instruction is switched to the discharging current instruction, so that the power failure fault of the battery side is judged, and after the judgment, the discharging current instruction is switched back to the charging current instruction, so that the floating charge state of the energy storage system is recovered; therefore, the power failure fault detection can be carried out in the floating state of the energy storage system through the switching of the current instruction, and the floating state of the energy storage system is not influenced or is little influenced.
Optionally, the second preset time is longer than the dc under-voltage protection time.
When the DC voltage is reduced to the critical voltage, the action of protecting the electric appliance, called undervoltage protection, has the task of mainly preventing the equipment from being burnt out due to overload. The second preset time is set to be longer than the direct-current undervoltage protection time, so that the electric device can be protected, and the problem caused by undervoltage is prevented.
The starting time points of the first preset time and the second preset time are the same, and the first preset time and the second preset time are the moments of switching to the discharge current instructions. The second preset time is longer than the first preset time, so that corresponding operation can be executed after the power failure fault is judged, and the operation is prevented from being too early.
It should be noted that, through the back and forth switching of the charging current instruction and the discharging current instruction, a judging cycle of the power failure fault can be completed, and the influence on the floating state of the energy storage system is small, so that the power failure fault of the battery pack can be detected under the condition that the normal floating state of the energy storage system is not influenced.
Optionally, the operation of a judging cycle of the power failure fault can be completed by switching the charging current command and the discharging current command back and forth, and the operation is repeatedly executed according to a fixed period, so that the power failure fault of the battery side can be periodically detected, and the condition of missing detection is avoided.
Optionally, as shown in fig. 3, in S200, after the energy storage system enters the floating state, before obtaining the reference voltage of the PCS dc side bus of the energy storage converter, the method further includes:
s100, acquiring current dispatching power and current power, battery side voltage and charging upper limit voltage of an energy storage system, and judging whether the energy storage system enters a floating charge state according to the current dispatching power, the current power, the battery side voltage and the charging upper limit voltage;
The operation of the PCS of the energy storage converter is carried out after a scheduling instruction of the energy storage system is received, wherein the scheduling instruction comprises scheduling power, and the scheduling power is the current scheduling power of the energy storage system; after the PCS of the energy storage converter receives the scheduling instruction, the power generated during specific execution is the current power of the energy storage system; the voltage at two ends of the battery side is the battery side voltage; the upper limit of the voltage (which is the upper limit of the voltage given in the instruction and is not the upper limit of the voltage that the battery side itself can bear) that the energy storage converter PCS receives to charge the battery side is the upper limit of the charge.
The normal scheduling logic of the PCS of the energy storage converter is that the battery side is charged or discharged according to the scheduling power in the received scheduling instruction; in addition, after receiving the battery-side charging command, the general command includes or the PCS pre-stores the target charging voltage, that is, the upper voltage limit, and when the battery-side voltage does not reach the upper voltage limit, the battery side is charged all the time.
Optionally, after all the following conditions are satisfied, determining that the energy storage system enters a floating state:
Condition one, the current power is less than 5% of the current scheduling power;
And in a second condition, the difference between the charging upper limit voltage and the battery side voltage is less than 5V.
Therefore, the floating state of the energy storage system can be directly judged, and the judgment accuracy is improved.
Optionally, as shown in fig. 4, the method for detecting power failure of the floating-charge battery of the energy storage system further includes:
And S600, after the power failure fault occurs on the battery side, controlling the PCS of the energy storage converter to stop running.
Therefore, after the power failure occurs at the battery side, the PCS of the energy storage converter is directly controlled to stop running, so that impact current caused by reclosing after the power failure of the battery can be avoided, and the safety of an operation system is improved.
Optionally, as shown in fig. 5, in S400, after a first preset time, a current dc side bus voltage is obtained, and whether a power failure occurs on the battery side is determined according to the dc side bus voltage and the dc side bus reference voltage, which includes:
s410, after a first preset time, acquiring the current direct-current side bus voltage;
S420, calculating the battery side power-down speed according to the first preset time, the direct-current side bus voltage and the direct-current side bus reference voltage;
The battery side voltage is changed from the direct current side bus reference voltage to the direct current side bus voltage in a first preset time, and the power failure speed of the battery side can be calculated according to the voltage.
After a charging current instruction of the PCS is switched to a discharging current instruction, if the DC side does not provide energy support by the battery, the PCS extracts energy from the DC side and can instantly pull down the upper voltage of the bus capacitor, namely the bus voltage of the DC side can be greatly reduced; however, if the DC side has battery support, the bus capacitor voltage will not change.
S430, if the power-down speed of the battery side is greater than a preset power-down speed threshold, judging that the power-down fault occurs on the battery side;
and S440, if the power-down speed of the battery side is smaller than the power-down speed threshold, judging that the power-down fault of the battery side does not occur.
The power-down speed of the battery side is larger than the power-down speed threshold value, which means that the bus voltage of the direct current side is obviously and greatly reduced, so that the battery side is determined to be not carrying out energy support on the direct current side, and the battery side has power-down fault; and if the power-down speed of the battery side is smaller than the power-down speed threshold, judging that the battery side supports the direct current side for energy, and the battery side does not have power-down faults.
Therefore, the power-down speed of the battery side is judged through the power-down speed threshold value, so that the power-down fault of the battery side is judged, and the method is simple, convenient and quick, and high in accuracy.
The power-down speed of the battery depends not only on the magnitude of the discharge current command, but also on the magnitude of the bus capacitor, and even further includes other parameters, which are not described herein. Therefore, the power-down speed threshold value on the battery side is also different in the case of the same magnitude of bus bar capacitance.
Optionally, in the case that the discharge current command is 10% of the PCS rated current of the energy storage converter, the power-down speed threshold is 15% of the reference voltage of the dc side bus dropped within 500 ms.
The following describes in detail a specific process of the method for detecting power failure of the battery in a floating state of the energy storage system with reference to fig. 6:
As shown in fig. 6, the battery side of the energy storage system is disconnected in a floating state, which is the same in characteristics as the floating state, and in the floating state, the reference voltage of the voltage ring is close to the bus voltage, the actual power of the energy storage converter PCS is limited by I REFA, and the energy storage converter PCS is kept in a continuous running state; if the battery is disconnected in the state, the PCS of the energy storage converter still keeps a continuous operation state, and the fact that the battery side of the whole system is disconnected or fails is not judged; after determining that the energy storage converter PCS enters the floating state, the instruction size for switching the instruction from I REFA to I REFB,IREFB may not be limited in a pulse form (the pulse width is not limited), but the direction of I REFB is limited, and the discharge direction is required; if the battery is full, after the instruction is switched from I REFA to I REFB, a short discharging process of the PCS occurs on the external characteristics, and after the discharging process is finished, the system is kept in a floating charge state; if the battery side is disconnected or the battery fails in the floating charge state, after the command is switched from I REFA to I REFB, the PCS bus voltage of the energy storage converter is pulled down because the direct current side does not provide energy support by the battery, so that the direct current side failure is reported.
Therefore, the battery power failure can be judged without increasing battery sampling data, and the DC side power is disturbed to carry out low-power discharge in a pulse form, so that the floating charge operation of the system is not influenced.
Fig. 7 is a schematic diagram of an energy storage system according to an embodiment of the application. The application also discloses an energy storage system, which comprises: an energy storage converter PCS10 and a battery 22;
one end of the energy storage converter PCS10 is connected with the output end of the storage battery 22, and the other end of the energy storage converter PCS is electrically connected with three phases of an alternating current power grid;
The PCS controller 12 is disposed in the energy storage converter PCS10, and the PCS controller 12 is communicatively connected to the storage battery 22 and is configured to perform the method for detecting a power failure of the floating battery of the energy storage system as described above.
Therefore, the external characteristics of the two conditions of disconnection of the battery side and disconnection of the battery side are obviously distinguished by switching the charging current instruction into the discharging current instruction, so that the power failure of the battery side is judged through the voltage of the direct current side, and the method is simple and convenient and has high accuracy; on the one hand, the method can be realized directly through the existing signal acquisition without acquiring a new type of electric signal; on the other hand, the actual electric energy consumption of the battery side is low, and the battery side is prevented from falling out of a floating state.
Therefore, the battery power failure can be judged without increasing battery sampling data, and the DC side power is disturbed to carry out low-power discharge in a pulse form, so that the floating charge operation of the system is not influenced.
The energy storage system further comprises a bus capacitor 21, and two ends of the bus capacitor are communicated with two input ends of the energy storage converter PCS 10.
The energy storage system further comprises a direct current side 20, wherein the direct current side 20 comprises a storage battery 22 and a bus capacitor 21.
The PCS controller 12 is connected to the battery 22 and the main power circuit 11 of the energy storage converter PCS10, and controls the battery 22 and the main power circuit 11.
Preferably, BCP and a battery cluster (not shown) may also be disposed in the battery 22, so as to detect and control a specific operation state of the battery cluster.
In the energy storage system, whether the battery side in the floating state is powered down is determined, and in fact, in the direct current power supply process according to the present application, the battery side in the floating state and the direct current source can be equally regarded, that is, the present application can be used to determine whether the battery side in the floating state is disconnected or not, and also determine whether the direct current source is disconnected or not when the battery side is the direct current source.
Although the present disclosure is described above, the scope of protection of the present disclosure is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the scope of the invention.
Claims (9)
1. The utility model provides a detection method is lost power to energy storage system float state battery, is applied to the energy storage system that contains energy storage converter PCS, and characterized in that includes:
After the energy storage system enters a floating charge state, acquiring a PCS direct-current side bus reference voltage of the energy storage converter;
switching a reference current instruction of the current loop into a preset discharge current instruction;
After a first preset time, acquiring current direct-current side bus voltage, judging whether a power failure occurs on a battery side according to the direct-current side bus voltage and the direct-current side bus reference voltage, and comprising the following steps: calculating the battery side power-down speed according to the first preset time, the direct-current side bus voltage and the direct-current side bus reference voltage; if the power-down speed of the battery side is greater than a preset power-down speed threshold, judging that the power-down fault occurs on the battery side; and if the power-down speed of the battery side is smaller than the power-down speed threshold, judging that the power-down fault of the battery side does not occur.
2. The method for detecting a power failure of a floating state battery of an energy storage system according to claim 1, further comprising:
Switching the discharge current command back to the reference current command of the current loop after a second preset time;
The first preset time and the second preset time are the same in starting time point, and are all the time points switched to the discharge current instruction, and the second preset time is longer than the first preset time.
3. The method for detecting power failure of a battery in a floating state of an energy storage system according to claim 1, wherein after the energy storage system enters the floating state, before obtaining the PCS dc side bus reference voltage of the energy storage converter, the method further comprises:
And acquiring the current dispatching power and the current power of the energy storage system, and the battery side voltage and the charging upper limit voltage, and judging whether the energy storage system enters a floating charge state according to the current dispatching power, the current power, the battery side voltage and the charging upper limit voltage.
4. The method for detecting power failure of a floating state battery of an energy storage system according to claim 1, wherein the specified current value in the discharging current command is less than 40% of the PCS rated current of the energy storage converter.
5. The method of claim 4, wherein the specified current value in the discharge current command is within 10% -20% of the PCS rated current of the energy storage converter.
6. The method for detecting power failure of a floating state battery of an energy storage system according to claim 3, wherein the energy storage system is determined to enter a floating state after all of the following conditions are satisfied:
condition one, the current power is less than 5% of the current scheduling power;
And in a second condition, the difference between the charging upper limit voltage and the battery side voltage is less than 5V.
7. The method for detecting power failure of a floating state battery of an energy storage system according to claim 2, wherein the second preset time is longer than a direct current under-voltage protection time.
8. The method for detecting a power failure of a floating state battery of an energy storage system according to claim 1, further comprising:
And after the power failure fault occurs at the battery side, controlling the PCS of the energy storage converter to stop running.
9. An energy storage system, comprising: an energy storage converter PCS (10) and a storage battery (22);
One end of the energy storage converter PCS (10) is connected with the output end of the storage battery (22), and the other end of the energy storage converter PCS is electrically connected with three phases of an alternating current power grid;
The PCS (10) is provided with a PCS controller (12), and the PCS controller (12) is communicatively connected to the storage battery (22) and is configured to perform the method for detecting a power failure of the floating battery of the energy storage system according to any one of claims 1 to 8.
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