High-voltage direct-current system and near-field multi-type reactive power compensation device cooperative control method thereof

Abstract

The invention discloses a high-voltage direct-current system and a near-area multi-type reactive power compensation device cooperative control method thereof. The method comprises the steps of reactive power compensation amount calculation; reactive compensation quantity distribution; calculating a passive compensation switching series; determining a passive compensation hierarchical coordination mode; determining an active compensation control mode; determining an active compensation reactive power reference value; and active power reference value matching. When reactive power fluctuates due to active power change and the like of the high-voltage direct-current power transmission system, multi-type reactive power compensation devices of the high-voltage direct-current power transmission system and a near-area alternating-current system of the high-voltage direct-current power transmission system are used for cooperative control, the reactive power compensation amount is accurately compensated, reactive power support of the high-voltage direct-current power transmission system is achieved, and the reactive power compensation efficiency is improved. Abnormal fluctuation of reactive power and alternating-current voltage is avoided, direct-current transmission capacity and efficiency are guaranteed, and reactive voltage stability of the system is maintained.

Description

Technical Field

[0001] The invention belongs to the field of high-voltage direct current power transmission, and relates to a high-voltage direct current system and a method for coordinated control of multiple types of reactive power compensation devices in its vicinity. Background Art

[0002] Ultra-high voltage direct current transmission technology is one of the important technologies in the current power transmission field. It has been widely used around the world for its advantages of large transmission capacity, long transmission distance and low loss. With the continuous growth of electricity demand and the improvement of power grid construction, the status of ultra-high voltage direct current transmission in the power system has gradually become prominent. However, while high-voltage direct current transmission can flexibly and efficiently transmit active power, it also consumes a large amount of reactive power. In addition, when the active power is adjusted, the reactive power will fluctuate, causing abnormal voltage fluctuations.

[0003] In order to solve the problems existing in the UHV DC transmission system, reactive power compensation technology came into being. Reactive power compensation is mainly to maintain the voltage stability of the system by providing the necessary reactive power. At home and abroad, the research on reactive power compensation technology has achieved remarkable results, and various types of reactive power compensation devices have emerged, such as reactive power capacitors, AC filters, and SVG. These devices have played an important role in improving the power factor of the power system, balancing the three-phase load, reducing voltage fluctuations, and suppressing harmonics. With the continuous development of reactive power compensation technology, various types of reactive power compensation devices have been widely used in power systems. These devices have their own characteristics. However, the simultaneous application of multiple reactive power compensation devices has also brought new problems. The adjustment of existing reactive power compensation equipment is passive, and there is no coordinated control between multiple types of reactive power compensation devices. There are problems such as reactive circulating current and reactive internal consumption, which leads to poor voltage control effect. How to coordinate and control these devices to achieve the optimal reactive power compensation effect has become a new challenge. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a coordinated control method for a high-voltage direct current system and its vicinity multiple types of reactive compensation devices, which comprehensively considers the characteristics of various reactive compensation devices, the actual needs of the power system and the operating status, so that the reactive power of the system can be quickly and accurately controlled through the coordinated cooperation of various types of reactive compensation devices, thereby maintaining the stability of the system reactive voltage, optimizing reactive compensation and solving the problem of coordinated control of multiple types of reactive compensation devices.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A high-voltage direct current system and a method for coordinated control of multiple types of reactive power compensation devices in its vicinity, comprising: obtaining system operation status information and active power adjustment instructions, calculating reactive power compensation requirements, allocating reactive power compensation requirements to passive reactive power compensation devices and active reactive power compensation devices for reactive power compensation, calculating matching active power adjustment instructions, and realizing active power adjustment in coordination with reactive power compensation.

[0007] Furthermore, it also includes: after allocating reactive power compensation demand to passive reactive power compensation device and active reactive power compensation device, calculating the switching level and hierarchical coordination mode of passive reactive power compensation device, and determining control mode and control instruction of active reactive power compensation device.

[0008] Further, the specific steps include:

[0009] Step 1: Calculate the reactive power compensation according to the following formula:

[0010]

[0011] Where: U PCC , P PCC , Q PCC are the AC voltage, active power and reactive power of the AC bus respectively; X ac is the reactance of the AC transmission line; ΔP and ΔQ are the active power change and reactive power compensation respectively; They are the power factor angles before and after the system state changes;

[0012] Step 2, according to the reactive compensation amount calculated in step 1, respectively allocating it to the passive reactive compensation device and the active reactive compensation device to realize reactive compensation;

[0013] Step 3, calculating the passive compensation switching level;

[0014] Step 4: Determine the passive compensation hierarchical coordination method;

[0015] Step 5, determining the active compensation control mode;

[0016] Step 6, determining the active compensation reactive power reference value;

[0017] Step 7: Active power reference value matching.

[0018] Furthermore, in step 2, the specific allocation method is as follows:

[0019]

[0020] Where: Q C_P , Q C_Iare the reactive power compensation targets allocated to the passive reactive power compensation device and the active reactive power compensation device respectively; a is the number of action groups of the passive reactive power compensation device; Q c The reactive power value provided by a single set of passive reactive power compensation devices; int(x) is the integer calculation of x.

[0021] Furthermore, in step 3, the passive compensation switching level is calculated as follows:

[0022] k=[1,a],k∈Z

[0023] The above formula indicates that the action of the passive reactive compensation device is realized in one step, or only one minimum passive reactive compensation device unit is acted at a time, or a combination of any several minimum passive reactive compensation device units, until all the passive reactive compensation devices that need to be acted are acted upon.

[0024] Furthermore, in step 4, the passive compensation hierarchical coordination method is as follows: the switching timing of the passive reactive power compensation device is carried out simultaneously with the active power adjustment, or is slightly ahead of the coordinated active power adjustment, or is slightly behind the coordinated active power adjustment.

[0025] Furthermore, in step 5, the active reactive power compensation control mode is determined by selecting a fixed reactive power control mode of the active reactive power compensation device to perform reactive power control.

[0026] Furthermore, in step 6, the Q calculated in step 2 is C_I As a control reference value for reactive power.

[0027] Furthermore, in step 7, the active power reference value is calculated in the following manner:

[0028]

[0029] Where Q C is the reactive power provided by the passive reactive power compensation device or the active reactive power compensation device, ΔP is the required change in reactive power reference value, and the active power reference value matching is performed by the following method:

[0030] P ref =P PCC +ΔP.

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] 1. When reactive power fluctuates due to active power changes in the HVDC transmission system, the present invention uses multiple types of reactive compensation devices of the HVDC transmission system and its nearby AC system for coordinated control to accurately compensate for reactive power compensation, thereby achieving reactive support for the HVDC transmission system, avoiding abnormal fluctuations in reactive power and AC voltage, ensuring the transmission capacity and efficiency of DC, and maintaining the reactive voltage stability of the system.

[0033] 2. Compared with the traditional power control strategy of high-voltage direct current transmission system, the method of the present invention is based on the calculation of reactive compensation amount during active power adjustment, uses passive reactive compensation equipment and active reactive compensation equipment for reactive compensation, and effectively utilizes the reactive compensation equipment in the power grid; the present invention coordinates and controls various reactive compensation devices configured in the power grid to achieve fast and accurate reactive compensation, and ensures the reactive margin of the power grid.

[0034] 3. The method of the present invention performs coordinated active power control and gives full play to the flexible transmission capability of the high voltage direct current transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A principle flow chart of a coordinated control method for a high-voltage direct current system and multiple types of reactive power compensation devices in its vicinity provided by the present invention;

[0036] Figure 2 To verify the wiring diagram of a high-voltage direct current power transmission system containing multiple types of reactive power compensation devices of the present invention. DETAILED DESCRIPTION

[0037] The technical solution provided by the present invention will be described in detail below in conjunction with specific embodiments. It should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0038] The multi-type reactive compensation devices referred to in the present invention need to include passive reactive compensation devices and active reactive compensation devices. Passive reactive compensation devices include but are not limited to reactive compensation capacitors and AC filters, and active reactive compensation devices include but are not limited to SVG, SVC, and synchronous phase regulators.

[0039] The overall process of the method of the present invention comprises the following steps:

[0040] 1) First, obtain the system's operating status information and active power adjustment instructions, calculate the reactive power compensation demand, and allocate the reactive power compensation demand to the passive reactive compensation device and the active reactive compensation device for reactive compensation. The passive reactive compensation device undertakes the main compensation target, and the active reactive compensation device ensures fast and error-free compensation.

[0041] 2) After confirming that the reactive power target allocation is completed, calculate the switching levels of capacitors / filters, the hierarchical coordination method of capacitors / filters, the control method of SVG and the control instructions of SVG;

[0042] 3) After allocating reactive power compensation demand to multiple types of reactive power compensation devices, the matching active power adjustment instructions are calculated and active power adjustment is achieved in conjunction with reactive power compensation.

[0043] During the coordination of multiple types of reactive power compensation, passive reactive power compensation devices and active reactive power compensation devices are used for reactive power compensation, and the adjustment of active power is coordinated to achieve accurate and rapid compensation of the system reactive power, increase the transmission efficiency of the high-voltage direct current system, and maintain the stability of the system reactive voltage.

[0044] Specifically, the high voltage direct current system and the coordinated control method of the near-area multi-type reactive power compensation device provided by the present invention include the following steps:

[0045] Step 1: Calculate the reactive power compensation amount; specifically, calculate according to the following formula:

[0046]

[0047] Where: U PCC , P PCC , Q PCC are the AC voltage, active power and reactive power of the AC bus respectively; X ac is the reactance of the AC transmission line; ΔP and ΔQ are the active power change and reactive power compensation respectively; They are the power factor angles before and after the system status changes. These parameters are obtained from the system operation status data.

[0048] Step 2, reactive power compensation allocation. This step is to allocate the calculated reactive power to the passive reactive power compensation device and the active reactive power compensation device to achieve accurate reactive power compensation. The allocation principle is to use the passive reactive power compensation device to switch on and off in stages and coordinate at multiple levels to bear more reactive power as much as possible, and use the active reactive power compensation device to accurately and quickly compensate for a small part of the reactive power. The specific allocation method is as follows:

[0049]

[0050] Where: Q C_P , Q C_I are the reactive power compensation targets allocated to the passive reactive power compensation device and the active reactive power compensation device respectively; a is the number of action groups of the passive reactive power compensation device; Q c The reactive power value provided by a single set of passive reactive power compensation devices; int(x) is the integer calculation of x.

[0051] Step 3, calculation of passive compensation switching levels; the calculation method is as follows:

[0052] k=[1,a],k∈Z

[0053] That is, the action of the passive reactive power compensation device can be realized in one step, or only one minimum passive reactive power compensation device unit can be actuated at a time, or a combination of any few minimum passive reactive power compensation device units can be actuated until all the capacitors / filter groups that need to be actuated are actuated.

[0054] Step 4, the passive compensation hierarchical coordination mode is determined; the switching timing of the passive reactive power compensation device can be carried out simultaneously with the active power adjustment, or slightly ahead of the coordinated active power adjustment, or slightly behind the coordinated active power adjustment.

[0055] Step 5, determining the active compensation control mode; the active reactive power compensation control mode is determined by selecting a fixed reactive power control mode of the active reactive power compensation device to perform reactive power control.

[0056] Step 6, active reactive compensation reference value determination; active reactive compensation reactive reference value determination is to calculate the Q in step 2 C_I As a control reference value for reactive power.

[0057] Step 7: Active power reference value matching. The active power reference value is calculated by:

[0058]

[0059] Where Q C is the reactive power provided by the passive reactive power compensation device or the active reactive power compensation device, ΔP is the required reactive power reference value change, and the active power reference value matching can be performed using the following method:

[0060] P ref =P PCC +ΔP.

[0061] Application examples:

[0062] Figure 2 This is a wiring diagram of a high-voltage direct current transmission system with multiple types of reactive compensation devices, including reactive compensation capacitors, AC filters and SVG. Capacitors and AC filters perform reactive compensation in the form of reactive groups, and SVG adopts a fixed reactive power control mode. The initial active power of the system is 200MW, the active adjustment target is 420MW, the DC voltage is ±200kV, the rated reactive power provided by the unit passive reactive compensation equipment is 40Mvar, and the capacitance and resistance of the AC transmission line are 7.99Ω and 10.20Ω respectively.

[0063] In the process of active power adjustment, the high voltage direct current system and the coordinated control method of the near-area multi-type reactive power compensation device thereof include the following steps:

[0064] 1) According to the active power adjustment instruction from 200MW to 420MW, as well as the system parameters such as DC voltage, the reactive power compensation demand is calculated to be 150.44MVar.

[0065] 2) According to the allocation method of reactive power compensation, the passive reactive power compensation equipment group is selected to undertake 120 MVar of reactive power compensation, which is achieved by investing three groups of passive reactive power compensation devices, and the active reactive power compensation equipment is responsible for compensating 30.44 MVar of reactive power compensation;

[0066] 3) The passive reactive power compensation device is selected to be put into operation at the same time as the active power adjustment, and the input compensation is 3, that is, one set of passive reactive power compensation devices is put into operation in each step, and the input is divided into 3 steps. The control mode of SVG is selected as fixed reactive power control, and the control reference value is set to +30.44MVar;

[0067] 4) The change process of the calculated coordinated active power reference value is from 200MW, adjusted to 260.18MW in coordination with the input of the first group of passive reactive compensation devices, then adjusted to 318.84MW in coordination with the input of the second group of passive reactive compensation devices, then adjusted to 375.99MW in coordination with the input of the third group of passive reactive compensation devices, and finally, the active power reference value is set to 420MW in coordination with the reactive compensation of SVG.

[0068] Compared with the traditional reactive power control which detects that the AC voltage of the AC bus exceeds the reference value and then activates the reactive power compensation device, which will introduce large reactive voltage fluctuations when the active power is adjusted, the present invention adopts active reactive power compensation and realizes accurate and rapid reactive power compensation based on the coordination between multiple types of reactive power compensation devices, thereby maintaining the stability of the system reactive voltage.

[0069] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A high voltage direct current system and a method for coordinated control of multiple types of reactive power compensation devices in its vicinity, characterized in that: include: Obtain the system's operating status information and active power adjustment instructions, calculate the reactive power compensation demand, allocate the reactive power compensation demand to the passive reactive compensation device and the active reactive compensation device for reactive compensation, calculate the matching active power adjustment instructions, and achieve active power adjustment in conjunction with reactive compensation.

2. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 1, characterized in that: Also includes: After allocating reactive power compensation demand to passive reactive power compensation device and active reactive power compensation device, calculate the switching level and hierarchical coordination mode of passive reactive power compensation device, and determine the control mode and control instruction of active reactive power compensation device.

3. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 1 or 2, characterized in that: The specific steps include: Step 1: Calculate the reactive power compensation according to the following formula: Where: U PCC , P PCC , Q PCC are the AC voltage, active power and reactive power of the AC bus respectively; X ac is the reactance of the AC transmission line; ΔP and ΔQ are the active power change and reactive power compensation respectively; They are the power factor angles before and after the system state changes; Step 2, according to the reactive compensation amount calculated in step 1, respectively allocating it to the passive reactive compensation device and the active reactive compensation device to realize reactive compensation; Step 3, calculating the passive compensation switching level; Step 4: Determine the passive compensation hierarchical coordination method; Step 5, determining the active compensation control mode; Step 6, determining the active compensation reactive power reference value; Step 7: Active power reference value matching.

4. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 2, the specific allocation method is as follows: Where: Q C_P , Q C_I are the reactive power compensation targets allocated to the passive reactive power compensation device and the active reactive power compensation device respectively; a is the number of action groups of the passive reactive power compensation device; Q c The reactive power value provided by a single set of passive reactive power compensation devices; int(x) is the integer calculation of x.

5. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 3, the passive compensation switching level is calculated as follows: k=[1,a],k∈Z The above formula indicates that the action of the passive reactive compensation device is realized in one step, or only one minimum passive reactive compensation device unit is acted at a time, or a combination of any several minimum passive reactive compensation device units, until all the passive reactive compensation devices that need to be acted are acted upon.

6. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 4, the passive compensation hierarchical coordination method is as follows: the switching timing of the passive reactive power compensation device is carried out simultaneously with the active power adjustment, or slightly ahead of the coordinated active power adjustment, or slightly behind the coordinated active power adjustment.

7. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 5, the active reactive power compensation control mode is determined by selecting a fixed reactive power control mode of the active reactive power compensation device to perform reactive power control.

8. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 6, the Q calculated in step 2 is C_I As a control reference value for reactive power.

9. The high voltage direct current system and the coordinated control method of multiple types of reactive power compensation devices in the vicinity thereof according to claim 3, characterized in that: In step 7, the active power reference value is calculated in the following manner: Where Q C is the reactive power provided by the passive reactive power compensation device or the active reactive power compensation device, ΔP is the required change in reactive power reference value, and the active power reference value matching is performed by the following method: P ref =P PCC +ΔP。

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