CN106452122A - Parallel coordinative running control method and control device of AC/DC direct current source - Google Patents

Abstract

The invention relates to an AC/DC direct current source parallel coordinated operation control method and a control device, which calculates the correction current of each AC/DC converter; calculates the current command value of each AC/DC converter; and then calculates each AC/DC converter The sum of the corrected current of the converter and the current command value of the corresponding AC/DC converter, and calculate the difference between the sum and the DC current of the corresponding AC/DC converter, the difference is the corresponding AC/DC converter The given value of the output current of each AC/DC converter is used to control the corresponding AC/DC converter according to the given value of the output current of each AC/DC converter, so as to realize the parallel coordinated operation control. The situation of circulating current is avoided, the reliable operation of the DC source is satisfied, and the output of each AC/DC converter can achieve the optimal conversion efficiency.

Description

AC/DC DC source parallel coordinated operation control method and control device

technical field

The invention relates to an AC/DC direct current source parallel coordinated operation control method and a control device, and belongs to the technical field of direct current source current equalization control.

Background technique

With the improvement of the single capacity level of power electronic equipment, the number of power electronic equipment with parallel structure is increasing. As shown in Figure 1, it is an existing DC source composed of multiple AC/DC converters connected in parallel. , the DC sides of these AC/DC converters are all connected to the DC bus. The capacity of this DC source has been greatly improved and the output power has been effectively increased. However, a big problem has also emerged.

Due to the different output impedances and no-load voltages of multiple AC/DC converters, it will lead to uneven current when the DC voltage control is performed on the same DC bus at the same time. However, there is a worse situation, that is, circulating current. It can be seen from the drooping characteristics of PWM rectification that the prerequisite for the occurrence of circulating current is that the no-load voltage of the converter is different. Under different conditions of satisfying the no-load voltage of multiple converters, when the difference of no-load voltage of multiple converters is larger, the probability of circulating current is greater, and the circulating current is larger; when the no-load voltage of multiple converters The load voltage is different, when the output impedance of multiple converters is smaller, the probability of circulating current is greater, and the circulating current is larger. Inconsistency in the internal resistance characteristics of each device causes the system to be used as a DC source in the case of a common DC bus, and power circulation will occur.

In order to effectively eliminate uneven current and commutation phenomena, the Chinese patent application with publication number CN 105048502A discloses a control method for a parallel power generation system. The output values are added together as the output current given value, and then current sharing control is performed according to the output current given value of each module. Among them, the output value of the voltage regulator of each module is obtained according to the difference between the output voltage reference value and the output voltage. Since the output voltage reference value is a fixed value, the output value of the voltage regulator corresponding to each module is related to the respective output voltage. , because the difference range of each output voltage may be relatively large, and the obtained output values of the voltage regulators of each module also have a correspondingly large difference. Therefore, this control method is inflexible and has low reliability.

Contents of the invention

The purpose of the present invention is to provide a method for controlling the coordinated operation of AC/DC sources in parallel to solve the problem of low control reliability of the existing current sharing control method. The invention also provides an AC/DC direct current source parallel coordinated operation control device.

In order to achieve the above object, the solution of the present invention includes a method for controlling the coordinated operation of AC/DC direct current sources in parallel, including:

The step of calculating the correction current of each AC/DC converter is specifically: calculating the average current according to the DC currents of all AC/DC converters, and calculating the average current with the DC current of each AC/DC converter The difference corresponds to the correction current of each AC/DC converter;

The step of calculating the current command value of each AC/DC converter is specifically: setting at least two voltage ranges, and correspondingly calculating the voltage range of each AC/DC converter according to the voltage range of the DC voltage of each AC/DC converter. The current command value of the converter;

The steps of parallel coordinated operation control are as follows: calculate the sum of the correction current of each AC/DC converter and the current command value of the corresponding AC/DC converter, and calculate the sum of the value and the corresponding AC/DC converter The difference of the DC current, the difference is the output current given value of the corresponding AC/DC converter, according to the output current given value of each AC/DC converter to the corresponding AC/DC converter Control to realize parallel coordinated operation control.

In the step of calculating the current command value of each AC/DC converter, different voltage ranges correspond to different calculation methods of the power output reference value, and the corresponding calculation is based on the voltage range of the DC voltage of each AC/DC converter. The power output reference value of each AC/DC converter, and then calculate the current command value of each AC/DC converter according to the power output reference value and the DC voltage of each AC/DC converter.

The voltage ranges are set to three, which are:

U _H1 ≤ U _dc < U _H2 , U _L1 ≤ U _dc < U _H1 and U _L2 ≤ U _dc < U _L1 ;

Calculate the power output reference value of each AC/DC converter according to the following formula:

Calculate the current command value of each AC/DC converter according to the following formula:

Among them, U _dc(i) is the DC voltage of the i-th AC/DC converter, U _H1 and U _L1 are the set control threshold voltages of the AC/DC converter respectively; U _H2 and U _L2 are the DC The upper and lower limits of the stable range of the bus voltage, U _H2 > U _H1 > U _L1 > U _L2 , P is the rated power of the AC/DC converter, _{Pre ref(i)} is the i-th AC/DC The power output reference value of the converter, I _dcref(i) is the current command value of the i-th AC/DC converter, i=1, 2, . . . , n.

A control device for parallel coordinated operation of AC/DC direct current sources, comprising:

The module for calculating the correction current of each AC/DC converter is specifically: calculate the average current according to the DC currents of all AC/DC converters, and combine the average current with the DC current of each AC/DC converter The current difference corresponds to the correction current of each AC/DC converter;

A module for calculating the current command value of each AC/DC converter, specifically: at least two voltage ranges are set, and each AC/DC converter is correspondingly calculated according to the voltage range of the DC voltage of each AC/DC converter. The current command value of the DC converter;

A module for parallel coordinated operation control, specifically: calculate the sum of the correction current of each AC/DC converter and the current command value of the corresponding AC/DC converter, and calculate the sum of the value and the corresponding AC/DC converter The difference between the DC currents of the converters, the difference is the given value of the output current of the corresponding AC/DC converter, according to the given value of the output current of each AC/DC converter to the corresponding AC/DC converter The controller is controlled to realize parallel coordinated operation control.

In the process of calculating the current command value of each AC/DC converter, different voltage ranges correspond to different calculation methods of the power output reference value, and each AC is calculated according to the voltage range of the DC voltage of each AC/DC converter. /DC converter power output reference value, and then calculate the current command value of each AC/DC converter according to the power output reference value and the DC voltage of each AC/DC converter.

The voltage ranges are set to three, which are:

U _H1 ≤ U _dc < U _H2 , U _L1 ≤ U _dc < U _H1 and U _L2 ≤ U _dc < U _L1 ;

Calculate the power output reference value of each AC/DC converter according to the following formula:

Calculate the current command value of each AC/DC converter according to the following formula:

Among them, U _dc(i) is the DC voltage of the i-th AC/DC converter, U _H1 and U _L1 are the set control threshold voltages of the AC/DC converter respectively; U _H2 and U _L2 are the DC The upper and lower limits of the stable range of the bus voltage, U _H2 > U _H1 > U _L1 > U _L2 , P is the rated power of the AC/DC converter, _{Pre ref(i)} is the i-th AC/DC The power output reference value of the converter, I _dcref(i) is the current command value of the i-th AC/DC converter, i=1, 2, . . . , n.

First, calculate the correction current of each AC/DC converter, and the current command value of each AC/DC converter, and then calculate the current value of each AC/DC converter based on the actual DC current of each AC/DC converter. The given value of the output current of each AC/DC converter, and finally according to the given value of the output current of each AC/DC converter, the corresponding AC/DC converters are controlled in parallel to coordinate the operation, so as to achieve the current of each AC/DC converter average effect. Therefore, the parallel coordinated control method provided by the present invention can avoid the occurrence of circulating current, satisfy the reliable operation of the DC source, and enable the output of each AC/DC converter to achieve optimal conversion efficiency. Moreover, compared with the existing coordinated control strategy that adopts the dominant DC bus voltage, the occurrence of inconsistency in the output power of each AC/DC converter is avoided.

Moreover, in the method provided by the present invention, at least two voltage ranges are set, and the current command value is calculated according to the voltage range of the DC voltage of the AC/DC converter, and the DC voltage is in different voltage ranges Corresponding to different acquisition methods of DC command values, this method can obtain a suitable current command value according to the voltage range of the DC voltage. Therefore, the method provided by the present invention is compared with existing In some methods, the reliability has been greatly improved. Moreover, no matter how large the difference between the DC voltages is, the appropriate current command value can be obtained according to a suitable calculation method. Therefore, the method provided by the present invention is more flexible in control, and is suitable for occasions where the DC voltage difference is large .

The control principle of the parallel coordinated control method provided by the present invention is the control of two DC current loops. In order to realize the DC current sharing control scheme, the DC current outer loop is used to adjust the power of the device itself, and the current inner loop is used to realize the system under unbalanced conditions. Its own current balance output is not affected by the state of the grid. Moreover, the outer loop adopts DC current loop control to ensure fast output response and balanced current distribution. Therefore, the present invention can realize the stable operation of the system, and can automatically adjust the control mode according to the characteristics of the DC bus parallel equipment to realize the current impact and power fluctuation when the system is started and cut off, and finally realize the output current balance.

Description of drawings

Figure 1 is a schematic diagram of the overall structure of a DC source composed of multiple AC/DC converters connected in parallel;

Fig. 2 is a droop characteristic curve;

Figure 3 is a schematic diagram of the overall structure of a DC source formed by two AC/DC converters connected in parallel;

Fig. 4 is a control schematic diagram of the parallel coordinated operation control method.

detailed description

method embodiment

The AC/DC direct current source parallel coordinated operation control method provided by the present invention is applicable to the direct current source system shown in Figure 1, wherein, n≥2, no matter what the specific value of n is, that is, how many DC sources are arranged in parallel All AC/DC converters can use the DC source parallel coordinated operation control method provided by the present invention to perform parallel coordinated control.

In this embodiment, the AC/DC converter in the AC/DC source is a bidirectional converter, as shown in FIG. When the energy provided by the DC/DC power supply is greater than the DC load, the AC/DC converter can absorb energy from the DC and input it to the AC grid. At this time, the converter works in the inverter state; otherwise, the absorbed energy from the AC is injected into the DC grid. At this time, the converter works in a rectifying state.

The AC/DC DC source parallel coordinated operation control method provided by the present invention mainly includes the following steps:

The step of calculating the correction current of each converter is specifically: using the existing current detection device to collect the DC current of each converter DC side, calculating the average value I av of all DC currents, and then calculating the average value I _av The difference between _av and the DC current of each converter is the corrected current value corresponding to each converter.

The step of calculating the current command value of each converter is specifically: detecting the DC voltage on the DC side of each converter, and the existing voltage detection device can be used for voltage detection. At least two voltage ranges are set, and the DC voltages of each AC/DC converter are in different voltage ranges, which correspond to different calculation methods of the current command value. Then, according to the DC voltage of each AC/DC converter The current command value of each AC/DC converter can be calculated. Since current has a corresponding relationship with power and voltage, in this embodiment, the current is calculated using the relationship between power and voltage, specifically: first, according to the voltage range of the DC voltage of each AC/DC converter, And calculate the power output reference value of each AC/DC converter according to the corresponding relationship between the voltage range and the power output reference value, and then according to the power output reference value of each AC/DC converter and the corresponding AC/DC converter The current command value of each AC/DC converter is calculated based on the DC voltage of the converter. This embodiment provides a specific calculation method, as follows:

In order to avoid unnecessary actions of the power electronic devices in the AC/DC converter and reduce the harmonics caused by the operation of the power electronic devices, the droop control characteristics of the AC/DC converter are shown in Figure 2.

Among them, U _H1 and U _L1 are the control threshold voltages of the AC/DC converter, which are set values; U _H2 and U _L2 are the upper and lower limits of the stable variation range of the DC bus voltage, that is, the DC bus voltage The maximum and minimum values that can be achieved when changing up and down are known values. This embodiment provides a specific relationship between the above parameters: U _H2 - U _H1 = 15V, U _L1 - U _L2 = 15V, U _H1 - U _L1 = 30V, of course, the present invention is not limited to this a specific relationship.

Since the AC/DC converter is a bidirectional AC/DC converter, its working modes are divided into three types:

1) Inverter mode: the power of the DC load is less than the rated power, the DC source operates under light load conditions, the DC bus voltage rises and exceeds U _H1 ; the AC/DC converter is turned on and works in the inverter mode, and the remaining The power is sent to the AC grid; when the DC bus voltage returns to U _H1 , the AC/DC converter stops working.

2) Standby mode: The DC bus voltage fluctuates in a small range around the rated value, and no power transmission is performed on the AC and DC sides.

3) Rectification mode: the DC load power is higher than the rated power, the DC source operates under heavy load, the DC bus voltage drops and is lower than U _L1 ; the AC/DC converter is turned on and works in the rectification mode, and the insufficient power inside the DC grid is supplied by the AC grid Supply; when the DC bus voltage returns to U _L1 , the AC/DC converter stops working.

Therefore, in this embodiment, there are three voltage ranges, which are:

U _H1 ≤ U _dc < U _H2 , U _L1 ≤ U _dc < U _H1 , and U _L2 ≤ U _dc < U _L1 .

According to the above droop characteristics, the active power output reference P _ref corresponding to each AC/DC converter can be obtained, and the calculation formula is as follows:

Among them, P is the rated power of the AC/DC converter, and P _ref is the power output reference value of the AC/DC converter. Different AC/DC converters have different power output reference values. Therefore, P _{ref (i)} represents the power output reference value of the i-th AC/DC converter, U _dc(i) is the DC voltage of the i-th AC/DC converter, i=1, 2, . . . , n.

Then calculate the current command value of each AC/DC converter according to the power output reference value, the calculation formula is as follows:

Wherein, I _dcref(i) is the current command value of the i-th AC/DC converter.

The above is to calculate the current command value according to the relationship between power and voltage, of course, other ways can also be used to calculate the current command value. No matter which method is used to calculate the current command value, the current command of each AC/DC converter is calculated according to the corresponding relationship between the voltage range of the DC voltage of each AC/DC converter and the current command value value.

The parallel coordinated operation control method also includes the step of parallel coordinated operation control. Parallel coordinated operation control is performed according to the corrected current value, current command value and actual DC current value of each AC/DC converter. Since all AC/DC converters have the same control strategy, one of them is taken as an example below ,details as follows:

Calculate the sum of the correction current of the AC/DC converter and the current command value of the AC/DC converter, and make a difference between the obtained sum and the actual DC current of the AC/DC converter, and the obtained difference The value is the given value of the output current of the AC/DC converter, and then the given value of the output current is processed to generate the corresponding PWM pulse wave to control the AC/DC converter, because this part belongs to Conventional technology is not described in detail here. The other AC/DC converters are also controlled in this way to realize the parallel coordinated operation control of the DC source.

When processing the output current given value to generate the corresponding PWM pulse wave, the three-phase current can be separated by positive and negative sequences to obtain positive and negative sequence components (because the device adopts a three-phase system, the output has no current zero-sequence component ),details as follows:

The separated positive and negative sequence components of the current are subjected to park rotation transformation to obtain the dq component. In this way, the PI control is used to realize the static-difference control of the DC flow and ensure the current is fast and stable. The details are as follows:

The above positive and negative sequence separation and rotation transformation belong to the conventional technology, and the focus of the present invention is not on this, so it will not be described in detail here.

Hereinafter, a representative n=2 is taken as an example for description. As shown in FIG. 3 , it includes an AC/DC converter 1 and an AC/DC converter 2 .

As shown in FIG. 4 , the DC source parallel coordinated operation control principle diagram provided by the present invention includes a current sharing loop and a current command loop. The current sharing loop is used to calculate the correction current of each converter, and the current command loop is used to calculate the current command value of each converter.

Collect the DC currents I _dc1 and I _dc2 of the two converters, and then obtain the average current I _av , and then make a difference between the average current I _av and the DC current I _dc1 of the converter 1 to obtain the corrected current of the converter 1 ΔI _dc1 , the difference between the average current I _av and the direct current I _dc2 of the converter 2 to obtain the corrected current ΔI _dc2 of the converter 2 .

The current command value I _dcref(1) of the converter 1 and the current command value I _dcref(2) of the converter 2 are respectively calculated according to the DC voltages of the two converters and the above calculation formula.

Then, the output current given value Iout1 of converter ₁ = ΔI _dc1 + I _dcref(1) -I _dc1 ; the output current given value Iout2 of converter ₂ = ΔI _dc2 + I _dcref(2) -I _dc2 .

Finally, the corresponding converters are controlled according to the obtained output current given values I _{output 1} and I _{output 2} to realize parallel coordinated operation control.

In addition, for the DC source in Figure 3, this embodiment also provides a control strategy for starting the DC source, specifically as follows: the DC parallel coordination control of the two converters accepts the starting command issued by the monitoring system at the same time, and the commutation When converter 1 receives the start command, the grid voltage meets the start conditions and starts to start first, and the DC voltage is stabilized; converter 2 receives the start command and judges whether the start of converter 1 is completed by detecting the current of converter 1 and the DC bus voltage of the port , after judging that the start-up of converter 1 is completed, the start-up of converter 2 is started.

Moreover, a control strategy for shutting down the DC source is also provided, specifically as follows: when the DC source receives a shutdown command, it starts to implement the current loop slow down power control, and when the current drops to a certain range, the converter 2 shuts down directly , if converter 1 receives the shutdown command in the same way as converter 2, in case of an emergency, converter 2 trips directly, and the output current of converter 1 is directly connected to the power output of converter 2. When the output power of converter 1 increases suddenly, overshoot will occur. When converter 1 encounters an emergency shutdown, it adopts the same side rate as converter 2. This shutdown scheme can avoid current jitter caused by power fluctuations during startup as much as possible.

In the above embodiments, a specific relationship between the voltage range of the DC voltage of each AC/DC converter and the current command value of the corresponding AC/DC converter is given, which is only a specific implementation mode, the present invention is not limited to the above-mentioned embodiments.

Device embodiment

The present invention also provides an AC/DC direct current source parallel coordinated operation control device, including the following modules: a module for calculating the correction current of each AC/DC converter; a module for calculating the current command of each AC/DC converter Value modules; modules for parallel coordinated operation control.

The above-mentioned three modules are all software modules, and their specific functions correspond to the three steps in the above-mentioned method embodiment. Since the above-mentioned method embodiment has already made a detailed description of these three steps, it will not be described in detail here. .

Specific embodiments have been given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention lies in the above-mentioned basic scheme. For those of ordinary skill in the art, according to the teaching of the present invention, it does not need to spend creative labor to design various deformation models, formulas, and parameters. Changes, modifications, substitutions and variations to the implementations without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims (6)

1. A kind of AC/DC direct current source parallel connection coordinated operation control method, is characterized in that, comprises: The step of calculating the correction current of each AC/DC converter is specifically: calculating the average current according to the DC currents of all AC/DC converters, and calculating the average current with the DC current of each AC/DC converter The difference corresponds to the correction current of each AC/DC converter; The step of calculating the current command value of each AC/DC converter is specifically: setting at least two voltage ranges, and correspondingly calculating the voltage range of each AC/DC converter according to the voltage range of the DC voltage of each AC/DC converter. The current command value of the converter; The steps of parallel coordinated operation control are as follows: calculate the sum of the correction current of each AC/DC converter and the current command value of the corresponding AC/DC converter, and calculate the sum of the value and the corresponding AC/DC converter The difference of the DC current, the difference is the output current given value of the corresponding AC/DC converter, according to the output current given value of each AC/DC converter to the corresponding AC/DC converter Control to realize parallel coordinated operation control. 2. the AC/DC source parallel coordinated operation control method according to claim 1, is characterized in that, In the step of calculating the current command value of each AC/DC converter, different voltage ranges correspond to different calculation methods of the power output reference value, and the corresponding calculation is based on the voltage range of the DC voltage of each AC/DC converter. The power output reference value of each AC/DC converter, and then calculate the current command value of each AC/DC converter according to the power output reference value and the DC voltage of each AC/DC converter. 3. the AC/DC direct current source parallel coordinated operation control method according to claim 2, is characterized in that, The voltage ranges are set to three, which are: U _H1 ≤ U _dc < U _H2 , U _L1 ≤ U _dc < U _H1 and U _L2 ≤ U _dc < U _L1 ; Calculate the power output reference value of each AC/DC converter according to the following formula: ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; P</span>}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; P</span>}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right.<span\; class="notranslate">\; ,</span>$ Calculate the current command value of each AC/DC converter according to the following formula: ${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ;</span>$ Among them, U _dc(i) is the DC voltage of the i-th AC/DC converter, U _H1 and U _L1 are the set control threshold voltages of the AC/DC converter respectively; U _H2 and U _L2 are the DC The upper and lower limits of the stable range of the bus voltage, U _H2 > U _H1 > U _L1 > U _L2 , P is the rated power of the AC/DC converter, _{Pre ref(i)} is the i-th AC/DC The power output reference value of the converter, I _dcref(i) is the current command value of the i-th AC/DC converter, i=1, 2, . . . , n. 4. A control device for parallel coordinated operation of AC/DC direct current sources, characterized in that it comprises: The module for calculating the correction current of each AC/DC converter is specifically: calculate the average current according to the DC currents of all AC/DC converters, and combine the average current with the DC current of each AC/DC converter The current difference corresponds to the correction current of each AC/DC converter; A module for calculating the current command value of each AC/DC converter, specifically: at least two voltage ranges are set, and each AC/DC converter is correspondingly calculated according to the voltage range of the DC voltage of each AC/DC converter. The current command value of the DC converter; A module for parallel coordinated operation control, specifically: calculate the sum of the correction current of each AC/DC converter and the current command value of the corresponding AC/DC converter, and calculate the sum of the value and the corresponding AC/DC converter The difference between the DC currents of the converters, the difference is the given value of the output current of the corresponding AC/DC converter, according to the given value of the output current of each AC/DC converter to the corresponding AC/DC converter The controller is controlled to realize parallel coordinated operation control. 5. The AC/DC direct current source parallel coordinated operation control device according to claim 4, characterized in that, In the process of calculating the current command value of each AC/DC converter, different voltage ranges correspond to different calculation methods of the power output reference value, and each AC is calculated according to the voltage range of the DC voltage of each AC/DC converter. /DC converter power output reference value, and then calculate the current command value of each AC/DC converter according to the power output reference value and the DC voltage of each AC/DC converter. 6. The AC/DC direct current source parallel coordinated operation control device according to claim 5, characterized in that, The voltage ranges are set to three, which are: U _H1 ≤ U _dc < U _H2 , U _L1 ≤ U _dc < U _H1 and U _L2 ≤ U _dc < U _L1 ; Calculate the power output reference value of each AC/DC converter according to the following formula: ${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}\mathrm{<span\; class="notranslate">\; P</span>}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}\\ \mathrm{<span\; class="notranslate">\; 0</span>}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; h</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; P</span>}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&le;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; <</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}\end{array}\right.<span\; class="notranslate">\; ,</span>$ Calculate the current command value of each AC/DC converter according to the following formula: ${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; e</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; ;</span>$ Among them, U _dc(i) is the DC voltage of the i-th AC/DC converter, U _H1 and U _L1 are the set control threshold voltages of the AC/DC converter respectively; U _H2 and U _L2 are the DC The upper and lower limits of the stable range of the bus voltage, U _H2 > U _H1 > U _L1 > U _L2 , P is the rated power of the AC/DC converter, _{Pre ref(i)} is the i-th AC/DC The power output reference value of the converter, I _dcref(i) is the current command value of the i-th AC/DC converter, i=1, 2, . . . , n.