CN-114498599-B - Energy coordination and neutral point balance control method applied to bidirectional energy storage converter

Abstract

The invention discloses an energy coordination and neutral point balance control method applied to a bidirectional energy storage converter, which specifically comprises the following steps: the voltage difference between the voltage dividing capacitor and the standard deviation value 0 of the bipolar direct current micro-grid is differed, a voltage-sharing control signal is generated after passing through the voltage regulator, the voltage-sharing control signal is differed from neutral point current, and an improved voltage-sharing control signal is generated as a result through the current regulator. The improved voltage equalizing control signal is added with the bus voltage control signal and then transmitted to the PWM pulse signal generator, and the pulse is generated to control the DC/DC converter. The invention adopts a method of a three-level bidirectional DC-DC energy storage converter to inhibit the problem of neutral point voltage deviation, and provides a voltage equalizing control loop with improved current loop. Compared with the traditional voltage equalizing control loop, the proposed voltage equalizing strategy has better effect on the problem of unbalanced voltage.

Inventors

• ZHANG HUI
• YU LU
• ZENG CHENG
• ZHANG ZECHUAN

Assignees

• 西安理工大学

Dates

Publication Date

20260505

Application Date

20211221

Claims (3)

1. 1. The energy coordination and neutral point balance control method applied to the bidirectional energy storage converter is characterized by comprising the following steps of: Step 1, designing bus voltage control and three-level DC/DC energy storage converter equalizing ring control according to the working principle of the three-level DC/DC energy storage converter, wherein the bus voltage control adopts traditional voltage and current double closed-loop control, and the method specifically comprises the following steps: Step 1.1, obtaining a DC bus voltage error value delta U according to a DC bus voltage rated value U N and a DC bus voltage feedback value U ref , wherein the DC bus voltage error value delta U is shown as a formula (1); (1); step 1.2, obtaining the current inner loop given value by the voltage error value DeltaU through the PI regulator , Obtaining a current error value delta I after making a difference with the inductance current feedback value of the energy storage side, wherein the current error value delta I is shown as a formula (2); (2); In the formula (2), I ref is the feedback current value of the inductance current at the energy storage side of the DC/DC converter; Step 1.3, generating a bus voltage control signal P by the current error value delta I through a current regulator; Step 1.4, the difference between the voltage of the voltage dividing capacitor and the standard deviation value 0 of the bipolar direct current micro-grid is subjected to difference to obtain a bipolar voltage error adjustment quantity delta U 1 , as shown in a formula (4); (4); Wherein, U NO is the voltage of the converter voltage-dividing capacitor C 1 , and U PO is the voltage of the converter voltage-dividing capacitor C 2 ; Step 1.5, the bipolar voltage error adjustment quantity DeltaU 1 is added with the bus voltage control signal P by the voltage equalizing control signal P 1 ;P 1 generated by the voltage regulator in the voltage division control, and a PWM modulation signal is obtained by the PWM regulator to control the switching tube of the converter; Step 2, adding improved current sharing control in the three-level DC/DC energy storage converter equalizing ring control, wherein the method specifically comprises the following steps: Step 2.1, extracting a bipolar direct current micro-grid neutral point current I 0 , and making a voltage equalizing control signal P 1 and a direct current micro-grid neutral point current I 0 to obtain a current difference value delta I 2 in a bipolar micro-grid equalizing control ring, wherein the current difference value delta I 2 is shown in a formula (6); (6); Step 2.2, the current difference Δi 1 is passed through the current regulator of the improved voltage sharing control loop to generate an improved voltage sharing control signal P 2 ; Step 2.3, adding the improved voltage equalizing control signal P 2 and the bus voltage control signal P, then obtaining a PWM modulation signal through a PWM regulator, and controlling a converter switching tube; and 2.4, controlling an IGBT switching tube of the DC/DC converter by a pulse signal generated by PWM to form closed-loop control of the double-level energy storage DC/DC converter.
2. 2. The method for controlling energy coordination and neutral point balance applied to a bi-directional energy storage converter according to claim 1, wherein in the step 1.5, the voltage regulator adopts a PI regulator with an equivalent transfer function G u (s), as shown in equation (5); (5); The Ku 1 is the proportional coefficient of the voltage-sharing control voltage loop, and the Ku 2 is the integral coefficient of the voltage-sharing control voltage loop.
3. 3. The method for controlling energy coordination and neutral point balance applied to a bi-directional energy storage converter according to claim 1, wherein in the step 2.2, the current regulator is a PI regulator, and the equivalent transfer function G ii (s) is as shown in formula (7); (7); Wherein, the K i1 is the proportional coefficient of the equalizing control current loop, and K i2 is the integral coefficient of equalizing control current.

Description

Energy coordination and neutral point balance control method applied to bidirectional energy storage converter Technical Field The invention belongs to the technical field of micro-grid energy storage converter control, and particularly relates to an energy coordination and neutral point balance control method applied to a bidirectional energy storage converter. Background With the continuous development of new energy, a distributed power generation technology (Distributed Generation, abbreviated as DG) mainly based on renewable energy, such as wind power generation, photovoltaic power generation and the like, has attracted wide attention due to the characteristics of flexible power generation mode, environmental compatibility and the like. In order to respond to the national call and exert the advantages of the distributed power generation technology and solve the problems of intermittence, randomness, dispersibility and the like of renewable energy sources, the concept of a micro-grid is proposed. Compared with an alternating-current micro-grid, the direct-current micro-grid can more efficiently and reliably receive renewable energy power generation systems such as wind and light, energy storage units, electric vehicles and other direct-current electric loads, and the direct-current micro-grid has no problems of power synchronization, harmonic waves and the like and is easy to control, so that the direct-current micro-grid has gained more attention in recent years. The bipolar direct current micro-grid formed by the double-bus structure not only has the common advantage of the direct current micro-grid, but also can select different buses to supply power according to different requirements of loads on power supply voltage, so that electric equipment with different voltage levels and distributed power supply access are more convenient, and the flexibility and reliability of the direct current power supply system can be further improved. In the direct current micro-grid, fluctuation of bus power can be caused by unstable output, load fluctuation and the like of the distributed power generation units, and the stability of a micro-grid system can be threatened when the fluctuation is serious. Reactive power does not exist in the direct current micro-grid, and the system power balance can be realized only by ensuring the stability of the direct current bus voltage, namely, the direct current bus voltage is the only index for measuring the stability of the system, so that how to stabilize the direct current bus voltage is the key point for researching the direct current micro-grid. The dc micro grid may be divided into a monopolar and a bipolar dc micro grid according to whether or not a neutral line exists. Compared with a unipolar direct current micro-grid, the bipolar direct current micro-grid provides more voltage class interfaces, the voltage class can be flexibly converted, and meanwhile, the utilization rate of the bipolar direct current micro-grid to the AC-DC converter is high. In addition, when one pole fails, the other pole can continue to operate, and the system has higher reliability and safety. However, unbalance of power supply, load, line parameters and the like of the positive electrode and the negative electrode can generate unbalanced current in a neutral line, so that line loss is increased, and meanwhile, the voltages of the bus bars of the positive electrode and the negative electrode deviate from rated values. When the load of a certain node is seriously unbalanced, the unbalance degree may exceed the standard, and even the unbalanced voltage protection of the neutral line is triggered. In order to flexibly adjust the voltage unbalance degree of the bipolar direct current micro-grid and ensure that the bus voltage operates in a reasonable range, a certain distributed cooperative control strategy is adopted to ensure the normal operation of the direct current load. Aiming at the unbalanced voltage suppression of a bipolar direct current micro-grid, the current strategy mainly comprises 3 types, namely ① adopting an AC-DC converter capable of suppressing the unbalanced voltage, ② installing a voltage balancer at an outlet of the AC-DC converter, and ③ adopting a load change-over switch to adjust the power supply polarity of a direct current load. The invention provides a control method for restraining unbalanced voltage of a direct current bus by adopting an energy storage three-level converter in a bipolar direct current micro-grid, so that the voltage of the positive electrode and the negative electrode of the direct current bus reach balance, and meanwhile, the bidirectional tide of the grid is realized. Disclosure of Invention The invention aims to provide an energy coordination and neutral point balance control method applied to a bidirectional energy storage converter, which adopts a grid-connected current feedback active damping method to inhibit resonance and improves robustness. Th