CN-122001035-A - Reactive quick response method of grid-structured energy storage converter

CN122001035ACN 122001035 ACN122001035 ACN 122001035ACN-122001035-A

Abstract

The invention discloses a reactive quick response method of a grid-structured energy storage converter, which skillfully realizes that transient support capacity is improved while steady-state current limiting is not influenced by connecting a high-pass filter in parallel on a virtual impedance voltage drop feedforward path. The steady-state component in the feedforward signal is effectively filtered through the high-pass filter, so that the current limiting effect of the virtual impedance in steady state is not weakened. Meanwhile, for the rapid current change in the transient process, the high-pass filter can enable the rapid current change to pass smoothly, so that the rapid support of output voltage is realized, the problem of steady-state current limiting failure caused by direct feedforward is avoided, and the defect of slow reactive transient response is overcome. The invention has higher flexibility, robustness and adaptability, can more stably and reliably improve the voltage source characteristic of the grid-structured energy storage converter, and provides more effective voltage support for the power grid.

Inventors

HUANG YANLE
LIU QING
Xiong Yufan
CHEN JIANLIANG

Assignees

河北工业大学

Dates

Publication Date: 20260508
Application Date: 20260130

Claims (6)

1. The reactive quick response method of the network-structured energy storage converter is characterized in that the network-structured energy storage converter is an LCL-type three-phase NPC three-level voltage source type inverter, the control mode of the converter is power outer loop and inner loop control, wherein the power outer loop adopts virtual synchronous machine control mode, the inner loop control is improved design, virtual impedance and a high-pass filter are added on the basis of voltage-current double closed loop control, inertia is provided for a power grid, and grid-connected point voltage is supported; The inner loop control comprises a voltage outer loop and a current inner loop, and comprises the following steps of firstly, connecting a virtual impedance in series in an inner loop control loop of a grid-built energy storage converter, and connecting a high-pass filter in parallel, wherein the inner loop control comprises an inner potential amplitude value output by a reactive loop controlled by a virtual synchronous machine The voltage drop on the virtual impedance is subtracted to obtain a reference voltage of a voltage outer loop, the reference voltage is subjected to difference with an actual output voltage, the obtained result is processed by a voltage outer loop PI regulator to generate a reference current of a current inner loop, then an inductor current value at an inverter side is collected in real time and is subjected to difference with the reference current, the obtained result is regulated by the current inner loop PI regulator to output a current loop control signal, meanwhile, the voltage drop on the virtual impedance is filtered by a high-pass filter to output a high-frequency dynamic component, namely a feedforward compensation signal, the current loop control signal is superposed with the feedforward compensation signal, the superposed signal is subjected to a modulation link to generate a switching control signal of the converter, and the converter is regulated and controlled according to the switching control signal, so that the reactive power quick response is realized.
2. The reactive fast response method of a grid-built energy storage converter of claim 1, wherein the design of virtual impedance parameters is guided according to formulas (20), (21); (20) (21) Wherein: for the peak value of the output voltage of the current transformer, Representing the current limit value of the current transformer; representing the virtual resistance; representing the virtual inductance; representing the power grid side inductance, namely the product of the inductance value of the power grid side inductance and the power grid voltage angular frequency; The impedance ratio representing the virtual impedance is represented, According to the setting Substituting the values of the virtual resistance and the virtual inductance into formulas (20) and (21) to obtain the values of the virtual resistance and the virtual inductance, and amplifying the values of the virtual resistance and the virtual inductance by 20% to obtain 、 Is a range of optimal values.
3. The reactive fast response method of a grid-formed energy storage converter of claim 1, wherein the voltage drop across the virtual impedance is calculated by first performing a coordinate transformation on a real-time acquired three-phase current signal of the inverter-side inductor, and converting the three-phase current signal into a synchronous rotating coordinate system, as shown in formula (22), wherein Represents a coordinate transformation matrix, adopts a form of constant amplitude transformation, Angular velocity representing synchronous rotation; (22) (23) Calculating voltage drop components on the dq-axis virtual impedance respectively by using the virtual impedance parameters, as shown in formula (24); (24) Wherein, the , Representing the virtual resistance; representing the virtual inductance.
4. The reactive fast response method of a grid-tied energy storage converter of claim 2, wherein the high pass filter transfer function is as shown in equation (25), wherein Represents the cut-off angular frequency of the high-pass filter; , the specific design of the cut-off frequency of the high pass filter may be written as equation (25) to equation (26): (26) Wherein the method comprises the steps of Indicating the cut-off frequency of the high-pass filter, Representing the frequency of the input signal, based on the rise time of the signal Bandwidth of Is of the formula (27): (27) For a low pass filter, there are ; The reactive power response time is obtained, and the cut-off frequency of the high-pass filter can be obtained according to the set reactive power response time And (3) reducing the maximum value by 1.5 times to obtain the optimal value range of the cut-off frequency of the high-pass filter.
5. The reactive fast response method of a grid-tied energy storage converter of claim 4, wherein in the virtual resistor Virtual inductance Within the optimal range of values of (c) and the cut-off frequency of the high-pass filter In the optimal value range, different values are calculated by a digital analog simulation method 、、 Active power output of grid-structured energy storage converter under value combination under different grid voltage drop conditions and reactive power response time, wherein the reactive power response time is not greater than a set value and the average value is minimum 、、 When the value combination with the minimum average value does not exist, screening out the value combination with the reactive power response time not larger than the set value under each power grid voltage drop condition, calculating the normalized average value of the reactive power response time under each value combination, and obtaining the minimum value combination as the optimal value 、、 The optimal value of the voltage is substituted into the inner loop control of the grid-structured energy storage converter, and reactive fast response can be realized when the voltage of the power grid drops.
6. The reactive fast response method of a grid-tied energy storage converter of claim 5, wherein the grid voltage sag is specifically set in a sag range from 3% to 90%.

Description

Reactive quick response method of grid-structured energy storage converter Technical Field The invention belongs to the technical field of new energy grid connection, and particularly relates to a reactive rapid response method of a grid-built energy storage converter. Background The risk of the operation reliability of the novel power system is increased under the background of double high, wherein the occurrence frequency of short circuit faults is highest, and the threat to the system is greatest. When the short-circuit fault is dealt with, the power generation unit avoids damage to the power generation unit caused by the short-circuit fault in an off-grid mode, so that voltage support cannot be provided for a power system, even the power grid fault is possibly aggravated, and a series of cascading reactions are caused. In order to improve the reliability of the power system for coping with short-circuit faults, industry standards at home and abroad require that the energy storage converter has low voltage ride through capability, and voltage support is provided for the power system while ensuring no off-grid during faults. The energy storage converter is a bridge for connecting the energy storage unit and the power grid, and can be divided into a following-net type energy storage converter and a net-structured energy storage converter. The equivalent impedance of the parallel-connected grid-type converter can be equivalent to a current source, and the parallel-connected grid-type converter depends on a phase-locked loop to track the frequency and the phase of a power grid. When the low-voltage fault is handled, a passive supporting mode is adopted, and corresponding reactive current needs to be output according to a current instruction. The grid-structured energy storage converter is power electronic equipment capable of autonomously establishing and maintaining the voltage and the frequency of a power grid. The grid-connected point voltage is independently constructed by simulating the external characteristics of the synchronous motor, the phase information of the grid-connected point voltage is obtained independently of the phase-locked loop, and the grid-connected point voltage appears as an equivalent impedance of a voltage source in series. When the low voltage ride through is dealt with, reactive current is actively generated to support grid-connected point voltage by means of externally displaying voltage source characteristics. It can be seen that the grid-connected converter has natural advantages for reactive power support of the power system during low voltage ride through, and has more obvious effect and faster response. At present, the requirements of the national power grid detection center on the low-voltage ride through test of the grid-formed energy storage converter can be mainly divided into two aspects, namely, on one hand, the reactive power is required to be compensated according to a set reactive voltage regulation coefficient when current limiting does not occur during the low-voltage ride through period of the grid-formed energy storage converter, the reactive power is required to be output to the greatest extent within the current limiting value when the output current limiting occurs, and on the other hand, the time from the voltage drop of the grid-formed energy storage converter to the establishment of the reactive current is required to be not more than 30 ms (see literature: national energy solar power generation research and development (experiment) center). In combination, this requires the grid-formed energy storage converter to provide as much reactive current as possible in as short a time as possible to achieve an effective support of the grid voltage. Although the grid-structured converter can respond to voltage drop in a short time, the reactive control strategy of the traditional grid-structured energy storage converter cannot establish reactive current with corresponding degree in a short time when the reactive control strategy is used for dealing with low voltage ride through, and the problem of insufficient reactive current response degree exists. The current literature mostly investigates the current limiting problem of the grid-built converter and generates reactive power as much as possible during fault steady-state to support the grid, but ignores the timeliness of the grid-built converter supporting the grid. Disclosure of Invention In order to overcome the defects of the prior art, the invention provides a reactive fast response method of a grid-structured energy storage converter, which skillfully realizes that the transient support capacity is improved while the steady-state current limiting is not influenced by connecting a high-pass filter in parallel on a virtual impedance voltage drop feedforward path. The invention solves the technical problems by designing a reactive quick response method of a grid-structured energy storage converter, wherein the