Automatic load sharing control method for parallel operation of two rectification generator sets of same type

Abstract

The invention relates to an automatic load sharing control method for parallel operation of two same-type rectification generator sets. The method comprises the following steps: calculating a no-load voltage value of an in-network unit; adjusting the voltage of the to-be-connected unit to be the same as the no-load voltage of the in-network unit; closing the unit to be connected in parallel; the bus voltage is adjusted, so that the voltage difference value between the current bus voltage and the rated voltage of the unit meets the voltage threshold requirement; after parallel operation, the bus voltage is monitored regularly, the voltage difference value is exceeded, the voltages of the two units are adjusted, and the voltage threshold requirement is ensured to be met. The power distribution technology of an alternating current system virtual difference method is used for reference, automatic power distribution of a small direct current power supply system is achieved, it is guaranteed that the power of two rectification generator sets is distributed according to the ratio, dynamic balance of load distribution of the two sets is maintained, and the system stability and the automation degree are improved.

Description

Technical Field

[0001] The invention relates to the technical field of power system control, and in particular to a method for automatically sharing loads when two rectifier generator sets of the same type are connected in parallel. Background Art

[0002] In the current AC power system, the virtual difference method power distribution technology is generally used to optimize the power distribution between the generator sets running in parallel. This method is achieved by installing a power converter and regulator on each generator and only installing one frequency converter in the entire system. The core idea is to reasonably distribute the load according to the preset ratio while keeping the grid frequency constant. The virtual difference method can ensure that although the speed regulator of each generator set running in parallel has a differential characteristic, the frequency of the grid can be kept constant and the power can be evenly distributed through adjustment to achieve a zero-difference effect. At present, there is no application of the virtual difference method power distribution technology in DC power systems. Summary of the invention

[0003] Aiming at the power distribution problem of DC power system, an automatic load sharing control method for two rectifier generators of the same type running in parallel is proposed. By drawing on the power distribution technology of virtual difference method in AC system, automatic power distribution of small DC power supply system is realized.

[0004] The technical solution of the present invention is: a method for automatically sharing load when two rectifier generator sets of the same type are connected in parallel, and the specific steps are as follows:

[0005] 1) Calculate the no-load voltage value of the grid-connected units;

[0006] 2) Adjust the voltage of the unit to be connected to the same level as the no-load voltage of the unit on the grid;

[0007] 3) Switch off the units to be paralleled;

[0008] 4) Adjust the bus voltage so that the voltage difference between the current bus voltage and the rated voltage of the unit meets the voltage threshold requirement;

[0009] 5) After parallel operation, the bus voltage is monitored regularly. If the voltage difference exceeds the value, the voltage of the two units is adjusted to ensure that the voltage threshold requirements are met.

[0010] Further, the step 1) is a method for calculating the no-load voltage value of the grid-connected unit:

[0011] Assume that the steady-state voltage regulation rate of two rectifier generator sets of the same type is k0, the voltage regulation pulse width is k1, the current power of the grid-connected units is P1, the system bus voltage is Um, and the no-load voltage value of the grid-connected units is U10:

[0012] U10=Um+P1×k0.

[0013] Further, the specific implementation method of step 2) is:

[0014] When the voltage of the unit to be connected is U2>U10, a voltage reduction signal is sent;

[0015] When the voltage of the unit to be paralleled is U2<U10, a voltage boost signal is sent;

[0016] The length of the voltage-regulated pulse width signal is = |U2-U10|×k1.

[0017] Further, the specific implementation method of step 4) is:

[0018] Calculate the difference between the current bus voltage Um and the rated voltage Ue of the unit, and send the same voltage regulation signal to the two units at the same time, so that the bus voltage is adjusted to within ±1% of Ue:

[0019] When Um>Ue, a voltage reduction signal is sent;

[0020] When Um<Ue, a boost signal is sent;

[0021] The length of the voltage-regulated pulse width signal is = |Um-Ue|×k1.

[0022] Furthermore, after the two units are operated in parallel, the load is automatically evenly distributed, and the bus voltage is monitored every 5 seconds. When the bus voltage exceeds the ±1% range of Ue, the same voltage regulation signal is sent to the two units at the same time for regulation.

[0023] The beneficial effects of the present invention are as follows: the automatic load sharing control method for two rectifier generator sets of the same type running in parallel ensures that the power of the two rectifier generator sets is distributed according to a ratio, maintains the dynamic balance of the load distribution of the two sets, and improves the system stability and automation level. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a load system topology diagram of two rectifier generator sets of the same type running in parallel in the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0026] Figure 1 The system shown in the figure proposes a control strategy for automatic and uniform load distribution after the units are connected in parallel. G1 and G2 are rectifier generator sets of the same model. The control method is:

[0027] 1. Calculate the no-load voltage value of the grid-connected units;

[0028] 2. Adjust the voltage of the unit to be connected to the same level as the no-load voltage of the unit on the grid;

[0029] 3. Switch on the combination of units to be paralleled;

[0030] 4. Adjust the bus voltage so that the voltage difference between the current bus voltage and the rated voltage of the unit meets the voltage threshold requirements; after parallel operation, monitor the bus voltage regularly, and if the voltage difference exceeds the value, adjust the voltages of the two units to ensure that the voltage threshold requirements are met.

[0031] Assume that the steady-state voltage regulation rate (the steady-state voltage regulation rate refers to the rate of change of the steady-state voltage of the synchronous generator under all load conditions from no-load to rated load) of two rectifier generators of the same type is k0 (V / kW), the voltage regulation pulse width is k1 (milliseconds / V), unit 1 is running on the grid, the current power is P1 (kW), the system bus voltage is Um (V), the voltage of unit 2 is U2, the system requires a voltage threshold value of 1%, and the control method for parallel operation is:

[0032] 1. Calculate the current no-load voltage value of unit 1:

[0033] U10=Um+P1×k0

[0034] 2. Adjust the voltage of unit 2 to U10:

[0035] When U2>U10, a voltage reduction signal is sent;

[0036] When U2<U10, a boost signal is sent;

[0037] The length of the voltage-regulated pulse width signal is = |U2-U10|×k1;

[0038] 3. Send the command to switch on the No. 2 generator group. After the No. 2 generator group switches on, the current power P1 will be evenly distributed.

[0039] 4. Adjust the bus voltage so that the voltage difference meets the voltage threshold requirements:

[0040] Calculate the difference between the current bus voltage Um and the rated voltage Ue of the unit (the rated voltage of the entire system, the two units are of the same model, and the system rated voltage is also equal to the rated voltage of the unit), and send the same voltage regulation signal to units 1 and 2 at the same time, so that the bus voltage is adjusted to within ±1% of Ue:

[0041] When Um>Ue, a voltage reduction signal is sent;

[0042] When Um<Ue, a boost signal is sent;

[0043] The length of the voltage-regulated pulse width signal is = |Um-Ue|×k1;

[0044] After the two units are connected in parallel, the load is automatically evenly distributed and the bus voltage is monitored every 5 seconds. When the bus voltage exceeds the ±1% range of Ue, the same voltage regulation signal is sent to the two units at the same time for regulation.

[0045] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for automatically sharing load when two rectifier generators of the same type are connected in parallel, characterized in that: The specific steps are as follows: 1) Calculate the no-load voltage value of the grid-connected units; 2) Adjust the voltage of the unit to be connected to the same level as the no-load voltage of the unit on the grid; 3) Switch off the units to be paralleled; 4) Adjust the bus voltage so that the voltage difference between the current bus voltage and the rated voltage of the unit meets the voltage threshold requirement; 5) After parallel operation, the bus voltage is monitored regularly. If the voltage difference exceeds the value, the voltage of the two units is adjusted to ensure that the voltage threshold requirements are met.

2. According to claim 1, the method for automatically sharing load when two rectifier-generator sets of the same type are connected in parallel is characterized in that: The calculation method of the no-load voltage value of the grid unit in step 1) is as follows: Assume that the steady-state voltage regulation rate of two rectifier generator sets of the same type is k0, the voltage regulation pulse width is k1, the current power of the grid-connected units is P1, the system bus voltage is Um, and the no-load voltage value of the grid-connected units is U10: U10=Um+P1×k0.

3. The method for automatically sharing load when two rectifier-generator sets of the same type are connected in parallel according to claim 2, characterized in that: The specific implementation method of step 2) is as follows: When the voltage of the unit to be connected is U2>U10, a voltage reduction signal is sent; When the voltage of the unit to be paralleled is U2<U10, a voltage boost signal is sent; The length of the voltage-regulated pulse width signal is = |U2-U10|×k1.

4. The method for automatically sharing load when two rectifier-generator sets of the same type are connected in parallel according to claim 3, characterized in that: The specific implementation method of step 4) is as follows: Calculate the difference between the current bus voltage Um and the rated voltage Ue of the unit, and send the same voltage regulation signal to the two units at the same time, so that the bus voltage is adjusted to within ±1% of Ue: When Um>Ue, a voltage reduction signal is sent; When Um<Ue, a boost signal is sent; The length of the voltage-regulated pulse width signal is = |Um-Ue|×k1.

5. The method for automatically sharing load when two rectifier-generator sets of the same type are connected in parallel according to claim 4, characterized in that: After the two units are connected in parallel, the load is automatically evenly distributed, and the bus voltage is monitored every 5 seconds. When the bus voltage exceeds the ±1% range of Ue, the same voltage regulation signal is sent to the two units at the same time for regulation.

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