Multi-target control method based on LCC-HVDC and near-field reactive power compensation device thereof

Abstract

The invention discloses a multi-target control method based on an LCC-HVDC and a near-area reactive power compensation device thereof. The multi-target control method comprises the following steps: acquiring an electrical quantity; obtaining an active power control instruction and an AC voltage control instruction; allocating AC voltage control tasks; determining an active reference value, and determining an action instruction of a reactive power compensation device; and issuing a control instruction. According to the invention, coordination control can be carried out on active equipment and reactive equipment of the LCC-HVDC system, multi-target control is realized, the power transmission capability of the system is improved, and safe and stable operation of the system is maintained. According to the method, the reactive compensation amount under the active power and alternating voltage targets is accurately calculated, the reactive compensation device in the system is reasonably utilized, the active power and the alternating voltage are controlled at the same time, the power transmission capacity of the system is improved, and safe and stable operation of the system is maintained.

Description

Technical Field

[0001] The invention belongs to the technical field of high voltage direct current transmission, and relates to a multi-objective control method based on LCC-HVDC and a near-zone reactive power compensation device. Background Art

[0002] In the power system, LCC-HVDC technology has become an important choice in the field of long-distance and large-capacity power transmission due to its significant advantages such as large transmission capacity, good operating stability, low system loss and low construction cost. However, with the increasing complexity of the power grid structure and the continuous growth of power demand, the LCC-HVDC system faces many challenges in active power control and AC voltage coordination. Since the thyristors used in LCC-HVDC are semi-controlled devices, they can only control active power and require reactive power compensation devices in the AC power grid to passively provide reactive power. Therefore, it is difficult to control the AC voltage while controlling active power. Traditional LCC-HVDC power control can only achieve active power control. When it is detected that the AC voltage fluctuation exceeds the reference value, the passive reactive compensation device is used to make the AC voltage return to the set range. This traditional power control method causes large fluctuations in the AC voltage, introduces fluctuations to the system, and limits the transmission capacity of LCC-HVDC.

[0003] The present invention coordinates active power control and AC voltage control, and utilizes the coordination between the action of the reactive power compensation device and the adjustment of the active power to make the active power and AC voltage of the LCC-HVDC reach the reference value. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a multi-objective control method based on LCC-HVDC and its vicinity reactive power compensation device, and based on the reactive power compensation device in the AC system to which the LCC-HVDC and its vicinity are connected, multi-objective control of active power and AC voltage is simultaneously achieved.

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

[0006] A multi-objective control method based on LCC-HVDC and its near-zone reactive power compensation device comprises the following steps:

[0007] Step 1: Collect electrical quantities;

[0008] Step 2: Obtain active power control instructions and AC voltage control instructions;

[0009] Step 3: Allocate AC voltage control tasks; including:

[0010] Calculate reactive power adjustment:

[0011] Based on the calculated reactive power adjustment amount, it is allocated to the reactive power compensation device configured in the AC near area for reactive power compensation;

[0012] By switching on or off capacitors and AC filters, as well as reactive power control of other reactive compensation devices, the reactive power provided by each reactive compensation device is made equal to the reactive power adjustment amount obtained by calculation;

[0013] Step 4: determining the active reference value and the reactive power compensation device action command;

[0014] Step 5: Control instructions are issued.

[0015] Furthermore, the step 1 includes: collecting the three-phase AC voltage U at the common coupling point of the LCC-HVDC system PCC , Active power P PCC and reactive power Q PCC , DC voltage U dc and DC current I dc , the trigger angle α of the converter valve, and the commutation angle μ.

[0016] Furthermore, the second step is: confirming the active power of the coordinated control refers to the control reference value P ref And AC voltage control reference value U ref .

[0017] Furthermore, in step three, the reactive power adjustment amount is calculated by the following formula:

[0018]

[0019] Where: X l is the reactance of the AC transmission line, and are the power factors before and after the coordinated control of the system, X c is the reactance of the connected reactive compensation capacitor and AC filter, and ΔQ is the required reactive power adjustment.

[0020] Furthermore, in step 3, the reactive power of the capacitor and the AC filter is calculated by the following formula:

[0021]

[0022] In the formula, Q c Reactive power provided by capacitors and AC filters.

[0023] Furthermore, the step four specifically includes: using the acquired active power reference value as a control reference value, and using a reactive compensation device in a nearby AC system to compensate for the reactive compensation amount calculated in step three.

[0024] Furthermore, when capacitors and AC filters are used for reactive power compensation, the number of capacitors and AC filters required is:

[0025]

[0026] When using SVG equipment for reactive power compensation, ΔQ is set as the reference value of SVG constant reactive power control.

[0027] Furthermore, the step five includes: sending the active power reference value to the fixed active power controller of the converter valve, and sending the reactive power compensation device action instruction to the reactive power compensation device.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] Through the control of LCC-HVDC active power and coordinated control of reactive power compensation devices in the system

[0030] 1. The present invention can coordinate the active equipment and reactive equipment of the LCC-HVDC system, realize multi-objective control, improve the power transmission capacity of the system, and maintain safe and stable operation of the system.

[0031] 2. The method of the present invention achieves the purpose of simultaneously controlling active power and AC voltage by accurately calculating the reactive compensation amount under active power and AC voltage targets and rationally utilizing the reactive compensation device in the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic flow chart of a multi-objective control method based on LCC-HVDC and its near-zone reactive power compensation device provided by the present invention.

[0033] Figure 2 The figure is a rectifier-side topology diagram of the LCC-HVDC and its nearby AC system to which the present invention is applicable. DETAILED DESCRIPTION

[0034] 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.

[0035] like Figure 1 As shown, the multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device provided by the present invention comprises the following steps:

[0036] Step 1: Electrical quantity collection: Collect the three-phase AC voltage U at the common coupling point of the LCC-HVDC system PCC , Active power P PCC and reactive power Q PCC , DC voltage Udc and DC current I dc , the trigger angle α of the converter valve, and the commutation angle μ.

[0037] Step 2: Obtain active power control instructions and AC voltage control instructions; confirm the active power control reference value P of the coordinated control ref And AC voltage control reference value U ref .

[0038] Step 3: Allocate AC voltage control tasks; specifically, the following process is included:

[0039] First, the reactive power adjustment amount is calculated by the following formula: In the active power adjustment instruction and the AC voltage adjustment instruction, the reactive power adjustment amount includes the reactive power loss of the AC transmission line, the reactive power absorbed by the converter valve, and the reactive power deviation of reactive compensation equipment such as capacitors and AC filters.

[0040]

[0041] Where: X l is the reactance of the AC transmission line, and are the power factors before and after the coordinated control of the system, X c is the reactance of the connected reactive compensation capacitor and AC filter, and ΔQ is the required reactive power adjustment.

[0042] Based on the calculated reactive power compensation amount, it is allocated to the reactive power compensation device configured in the AC near area for reactive power compensation.

[0043] The reactive power of capacitors and AC filters and the AC voltage command value have the following relationship:

[0044]

[0045] In the formula, Q c Reactive power provided by capacitors and AC filters.

[0046] By switching capacitors and AC filters on or off, as well as reactive power control of other reactive compensation devices in the system, the reactive power provided by each reactive compensation device is made equal to the calculated reactive compensation amount.

[0047] Step 4: Determine the active reference value and the reactive compensation device action command. The acquired active power reference value is sent to the active power controller of the converter valve as a control reference value. The reactive compensation amount calculated in step 3 is compensated by the reactive compensation device in the nearby AC system. When using capacitors and AC filters for reactive compensation, the number of capacitors and AC filters required is:

[0048]

[0049] When using SVG and other equipment for reactive power compensation, ΔQ is set as the reference value of SVG fixed reactive power control.

[0050] Step 5: Sending control instructions: Sending active power reference value and reactive power compensation device action instructions to the controller of the converter valve and the reactive power compensation device respectively.

[0051] The present invention collects electrical quantities and confirms the active power of coordinated control to control the reference value P ref And AC voltage control reference value U ref， Calculate the reactive power demand. Then, control the reactive power compensation equipment in the system so that the reactive power provided by the reactive power compensation equipment is equal to the reactive power demand. When using capacitors and AC filters for reactive power compensation, calculate the number of capacitors and AC filters required and switch them on and off by group. When using SVG and other equipment for reactive power compensation, set ΔQ as the reference value of SVG's fixed reactive power control. Finally, the active power control action is to set the active power reference value of LCC-HVDC to P ref The AC voltage control action is to adjust the AC voltage to U through the action of the reactive power compensation device. ref .

[0052] 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 multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device, characterized in that: The steps include: Step 1: Collect electrical quantities; Step 2: Obtain active power control instructions and AC voltage control instructions; Step 3: Allocate AC voltage control tasks; including: Calculate reactive power adjustment: Based on the calculated reactive power adjustment amount, it is allocated to the reactive power compensation device configured in the AC near area for reactive power compensation; By switching on or off capacitors and AC filters, as well as reactive power control of other reactive compensation devices, the reactive power provided by each reactive compensation device is made equal to the reactive power adjustment amount obtained by calculation; Step 4: determining the active reference value and the reactive power compensation device action command; Step 5: Control instructions are issued.

2. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: The step 1 comprises: collecting the three-phase AC voltage U at the common coupling point of the LCC-HVDC system PCC , Active power P PCC and reactive power Q PCC , DC voltage U dc and DC current I dc , the trigger angle α of the converter valve, and the commutation angle μ.

3. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: The second step is to confirm the active power control reference value P of the coordinated control ref And AC voltage control reference value U ref .

4. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: In step 3, the reactive power adjustment amount is calculated by the following formula: Where: X l is the reactance of the AC transmission line, and are the power factors before and after the coordinated control of the system, X c is the reactance of the connected reactive compensation capacitor and AC filter, and ΔQ is the required reactive power adjustment.

5. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: In step 3, the reactive power of the capacitor and the AC filter is calculated by the following formula: In the formula, Q c Reactive power provided by capacitors and AC filters.

6. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: The step 4 specifically includes: using the acquired active power reference value as a control reference value, and using a reactive power compensation device in a nearby AC system to perform compensation according to the reactive power compensation amount calculated in the step 3.

7. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 or 6, characterized in that: When capacitors and AC filters are used for reactive power compensation, the number of capacitors and AC filters required is: When using SVG equipment for reactive power compensation, ΔQ is set as the reference value of SVG constant reactive power control.

8. The multi-objective control method based on LCC-HVDC and its near-area reactive power compensation device according to claim 1 is characterized in that: The step five includes: sending the active power reference value to the fixed active power controller of the converter valve, and sending the reactive power compensation device action instruction to the reactive power compensation device.

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