CN-115714412-B - Micro-grid energy storage system current-limiting black start method and device

CN115714412BCN 115714412 BCN115714412 BCN 115714412BCN-115714412-B

Abstract

The invention relates to a method and a device for limiting current and black start of a micro-grid energy storage system. The method comprises the steps of S1, closing an incoming line alternating current breaker of an energy storage system, starting the energy storage system by constant frequency and constant voltage control to enable a voltage reference value to increase, S2, comparing a load current I in the energy storage system with a limiting value I limit of the load current, starting a current limiting PI controller to limit current when the comparison result is I > I limit , entering S3, judging whether the energy storage system is in a current limiting state when the comparison result is I≤I limit , entering S4, judging whether the result is negative, entering S5, S3, judging whether the load current is smaller than an expected value I ref of the load current, judging whether the result is negative, continuing to limit current, if so, closing the current limiting PI controller to stop limiting, entering S4, starting a voltage recovery mechanism to recover the voltage reference value to a value before current limiting, S5, continuing to increase the voltage reference value, S6, repeating the steps S2-S5 until the voltage reference value of the energy storage system reaches a set value, and black starting is completed.

Inventors

HAN JIAN
WANG YICHAO
WANG BAOGUI
HU YUKUAN

Assignees

新源智储能源发展(北京)有限公司

Dates

Publication Date: 20260508
Application Date: 20221101

Claims (9)

1. A micro-grid energy storage system current limiting black start method, the method comprising: S1, closing an incoming line alternating current breaker of an energy storage system, and starting the energy storage system by adopting constant-frequency and constant-voltage control to increase a voltage reference value; S2, comparing a load current I in the energy storage system with a limiting value I limit of the load current, wherein when the comparison result is I > I limit , starting a current-limiting PI controller to limit the current, and entering a step S3; S3, judging whether the load current is smaller than an expected value I ref of the load current, if not, continuing to limit the current, if so, closing the current-limiting PI controller to stop the current limiting, and entering step S4; S4, starting a voltage recovery mechanism to recover the voltage reference value to a value before current limiting; S5, continuously increasing the voltage reference value; S6, repeating the steps S2-S5 until the voltage reference value of the energy storage system reaches a set value, and completing black start; In the step S2, the current limiting PI controller is turned on to perform current limiting, which specifically includes: inputting a difference value I ek between an expected value I ref of the load current and the load current I into a current-limiting PI controller to obtain a voltage value delta U out required to be reduced by a voltage reference value of an energy storage system; Subtracting DeltaU out from the voltage reference value as a new voltage reference value to reduce the load current for current limiting, and recording the voltage reference value before current limiting.
2. The method for limiting current to a black start of an energy storage system of a micro-grid according to claim 1, wherein the method further comprises checking parameters related to the energy storage system in step S0. to confirm that the black start is started to the energy storage system, specifically comprising: s0-1, checking the switching state of the PCC point and judging whether the PCC point is in a disconnection state, if not, continuing checking and judging, and if so, entering the step S0-2; and S0-2, judging whether the three-phase alternating voltage is lower than M times of rated voltage, wherein M is 0.04-0.06, returning to the step S0-1 if the judgment result is negative, starting black start if the judgment result is positive, and entering the step S1.
3. The method for limiting current to black-start of an energy storage system of a micro-grid according to claim 1, wherein the constant frequency and constant voltage control in the step S1 comprises starting an ac voltage by a zero voltage soft start mode and respectively adopting independent PI control for the amplitude of the three-phase ac voltage.
4. The method for starting the ac voltage by the zero voltage soft start mode according to claim 3, wherein the method specifically comprises controlling the ac voltage reference value to gradually increase from 0 according to a set rate of change until reaching a set value U exp .
5. The method for limiting current to black-start of a micro-grid energy storage system according to claim 3, wherein the adjusting the amplitude of the three-phase ac voltage by using independent PI controllers comprises: collecting line voltage of alternating current of an energy storage system and converting to obtain three-phase alternating voltage amplitude; the amplitude of each alternating current voltage is differenced from the corresponding expected voltage amplitude, and the difference is input into a corresponding PI controller, so that the voltage difference value required to be adjusted is obtained; And summing the voltage difference value to be regulated with the respective expected voltage amplitude value to obtain the regulated three-phase alternating-current voltage amplitude value.
6. The micro-grid energy storage system current limiting black start method according to claim 1, wherein the expected value I ref of the load current is k times the limit value I limit of the load current, wherein 0< k <1.
7. The method for limiting the current to black start of the micro-grid energy storage system according to claim 1, wherein the voltage recovery mechanism gradually reduces the output of the current limiting PI controller to 0 in a linear recovery manner, so that the voltage reference value is recovered to a value before current limiting.
8. A micro-grid energy storage system current limiting black start device, the device comprising: The constant frequency and constant voltage control module is used for starting the energy storage system by adopting constant frequency and constant voltage control; The load current acquisition comparison module is used for comparing the load current I in the energy storage system with the limit value I limit and the expected value I ref of the load current after the energy storage system is started; The current limiting module is used for starting the current limiting PI controller to limit current when the load current I is larger than a limiting value I limit of the load current, closing the current limiting PI controller to stop the current limiting when the load current I is smaller than an expected value I ref of the load current, and concretely comprises inputting a difference value I ek between the expected value I ref of the load current and the load current I into the current limiting PI controller to obtain a voltage value delta U out which needs to be reduced for the voltage reference value of the energy storage system, subtracting the voltage reference value delta U out as a new voltage reference value to reduce the load current and record the voltage reference value before the current limiting, and And the voltage recovery module is used for starting a voltage recovery mechanism to recover the voltage reference value to a value before current limiting when the load current I is not greater than the limit value I limit of the load current after current limiting is started.
9. The micro-grid energy storage system current limiting black start device of claim 8, further comprising a state identification module for checking energy storage system related parameters and confirming that black start is initiated to the energy storage system.

Description

Micro-grid energy storage system current-limiting black start method and device Technical Field The invention relates to the field of black start of micro-grid energy storage systems, in particular to a method and a device for limiting current of a micro-grid energy storage system. Background 1.1 Background art With the development of distributed energy power generation technology, micro-grid control technology has also been a great advance. The micro-grid can be used as a controllable unit to realize self-control and protection, and can effectively coordinate the relation between the distributed power supply and the large power grid to realize rapid development of the power grid. The black start refers to that after the whole system is stopped due to failure, the system is completely powered off (the isolated small power grid is not excluded and still keeps running) and is in a full black state, and the system is not dependent on other network assistance, and a generator set with self-starting capability in the system is started to drive the generator set without self-starting capability, so that the recovery range of the system is gradually enlarged, and finally the recovery of the whole system is realized. When the micro-grid independently operates, the energy storage system is used as a main power supply and is required to have black start construction site energy, the micro-grid generally contains a large amount of click loads, the maximum 5-7 times of overcurrent occurs in the starting process, the black start failure of the micro-grid is caused, and the energy storage system in the prior art is used as the main power supply to realize the self-operation of the micro-grid, so that the following technical problems exist: in the black start process, partial load needs to be cut off first, and then the energy storage system is gradually put into the process after the black start is finished, so that the energy storage system has insufficient black start load capacity, the black start time of the micro-grid is prolonged, and inconvenience is brought to operation. 1.2 Prior Art related to the invention 1.2.1 Technical solution of the prior art one The technical scheme of the black start method of the isolated optical storage micro-grid taking the limit of the capacity of a storage battery into consideration is that a diesel generator is used as a black start power supply, an energy storage system is used as a non-black start power supply, all loads in the micro-grid are cut off before black start, the black start power supply is started, the voltage and the frequency of the micro-grid system are built, and then the loads are gradually put into operation. 1.2.2 Disadvantages of the prior art one According to the technical scheme, the black start of the micro-grid is realized by switching loads, so that the operation complexity and the black start time of the black start process are increased, meanwhile, the loads are firstly classified, the loads and the load grades of the micro-grid are not unchanged, and the later operation and maintenance are also difficult. 1.3 Prior Art II related to the invention 1.3.1 Technical solution of the second prior art The technical scheme provides a black start method which does not depend on residual electric quantity of a battery and residual fuel of a diesel generator, and uses solar energy to supply power to a converter control board, a battery management system control board and an energy storage inverter control board before black start, then closes a direct current breaker to carry out black start. 1.3.2 Disadvantages of the second prior art The technical scheme provides power for each control panel through solar energy and is ready for black start, but does not mention how the direct current inverter and the energy storage system work and how the direct current inverter and the energy storage system should work when more motor loads exist in the load. 1.4 Prior Art III related to the invention 1.4.1 Technical solution of the third prior art The method for black start of the micro-grid of the Chinese patent with the publication number of CN106356892A comprises the steps of obtaining the residual capacity of an energy storage battery of each micro-source to be started, generating a black start sequence according to the sequence of the residual capacity of the energy storage battery of each micro-source to be started, wherein the residual capacity of the energy storage battery of each micro-source to be started is larger than a preset capacity value, obtaining the number of micro-sources to be started in the black start sequence, judging whether the number of micro-sources to be started in the black start sequence is in a preset number range or not, if yes, sequentially starting the micro-sources to be started in the black start sequence according to the black start sequence, judging whether the micro-sources to be started in the black start sequence are started, and if