Variable frequency electric drive drilling rig MCC bus voltage boost control system and control method

Abstract

The application discloses a variable frequency electric drive drilling rig MCC bus voltage lifting control system, which comprises a control module A, a control module B, a synchronous detection module, a voltage conversion module, a filter module, a circuit breaker A, a transformer and a circuit breaker B; the control module A is connected with the control module B through a communication cable, the voltage conversion module is connected with the control module B through a communication optical fiber, the control module B is connected with the filter module through the synchronous detection module, the input end of the voltage conversion module is connected with the common DC bus of a variable frequency electric drive drilling rig electric control system, the output end of the voltage conversion module is connected with the input end of the filter module, the output end of the filter module is connected with the primary side of the transformer through the circuit breaker A, the secondary side of the transformer is connected with the MCC bus through the circuit breaker B; and the problem of MCC bus voltage being too low caused by various reasons such as insufficient industrial power grid capacity, long power transmission distance, heavy MCC system load or low power factor is solved.

Description

Technical Field

[0001] This invention belongs to the technical field of power systems for petroleum electric drilling rigs, and relates to a voltage boosting control system for the MCC bus of a variable frequency electric drive drilling rig.

[0002] This invention also relates to a method for controlling the voltage boost of the MCC bus in a variable frequency electric drive drilling rig. Background Technology

[0003] Traditional oil drilling rigs are powered by a small, independent power grid system connected to a diesel generator set. The main generator's AC 600V power supply is transmitted to the AC 400V MCC system via an AC 600V / 400V transformer. The MCC's load mainly consists of non-speed-regulating AC asynchronous motors (with relatively low load rates and power factors), so the supply voltage is generally not an issue. Furthermore, given that the rig operates in the field, the power quality requirements are not too high; it is sufficient to ensure the normal operation of all equipment and not significantly affect its lifespan.

[0004] Currently, to save drilling costs and achieve energy conservation, environmental protection, and emission reduction, a large number of oil drilling rigs are powered by grid electricity. Typically, a high-voltage room is added at the well site, and the AC 600V power required by the oil drilling rig is provided by a 10kV / 600V main transformer in the high-voltage room, with the 10kV sourced from the social or industrial power grid. Although grid electricity has many advantages in the oil drilling industry, due to various reasons, the voltage amplitude from the social or industrial power grid to the well site is often low, and heavy drilling loads can also cause voltage drops. This leads to the problem of low AC 400V MCC bus voltage in many drilling rig electrical control systems.

[0005] The low 10kV power supply input voltage at the well site leads to a low AC600V main power supply voltage. While this affects the main frequency converter and main motor of the oil drilling rig's electrical control system, it will not cause equipment failure, shutdown, or damage. The main motors can still operate at reduced speed and power despite the voltage drop. Due to vector control, the motors operate in a constant torque state and can still drive the load, albeit with reduced output power. However, a drop in the AC400V MCC bus voltage increases the current and copper losses of the AC motors on the MCC load side. If the voltage drop exceeds 10%, the motor winding temperature may rise, damaging the insulation or even burning out. If the living area also draws power from the MCC bus, the voltage drop in the living area, being far from the well site (usually over 1000 meters), results in an even more abnormally low power supply voltage, severely impacting the operation of electrical facilities and frequently causing household appliances to burn out. For control equipment and sensitive electrical equipment, when the voltage is too low, it may cause the frame circuit breaker to trip falsely, and various control circuits to malfunction, fail or even be damaged, affecting or endangering the stable operation of the electrical control system. Conventional drilling rig electrical control systems are powerless to deal with this.

[0006] Therefore, it is evident that low MCC bus voltage has become a significant factor affecting the normal operation of the electrical control system of electrically driven oil drilling rigs. Consequently, developing a cost-effective, compact device (capable of integration into the electrical control system) that can effectively boost the MCC bus voltage of electrically driven oil drilling rigs to prevent control system malfunctions caused by low voltage is of paramount importance. Summary of the Invention

[0007] The purpose of this invention is to provide a variable frequency electric drive drilling rig MCC bus voltage boosting control system, which solves the problem of low MCC bus voltage caused by various reasons such as insufficient industrial power grid capacity, long transmission distance, heavy load of MCC system or low power factor.

[0008] Another objective of this invention is to provide a method for controlling the voltage boosting of the MCC bus in a variable frequency electric drive drilling rig.

[0009] The first technical solution adopted in this invention is a variable frequency electric drive drilling rig MCC bus voltage boosting control system, including control module A, control module B, synchronization detection module, voltage conversion module, filtering module, circuit breaker A, transformer and circuit breaker B;

[0010] Control module A is connected to control module B via a communication cable. The voltage conversion module is connected to control module B via a communication fiber optic cable. Control module B is connected to the filter module via a synchronization detection module. The input terminal of the voltage conversion module is connected to the common DC bus of the variable frequency electric drive drilling rig's electrical control system. The output terminal of the voltage conversion module is connected to the input terminal of the filter module. The output terminal of the filter module is connected to the primary side of the transformer via circuit breaker A. The secondary side of the transformer is connected to the MCC bus via circuit breaker B.

[0011] The second technical solution of the present invention is a method for boosting the MCC bus voltage of a variable frequency electric drive drilling rig, which adopts a variable frequency electric drive drilling rig MCC bus voltage boosting control system and is implemented according to the following steps:

[0012] Step 1: Control module A determines whether the rectifier cabinet is running, and then controls circuit breaker A and voltage conversion module through control module A and control module B respectively;

[0013] Step 2: Increase the MCC bus voltage by determining whether the MCC bus voltage is lower than 360V and the DC bus voltage is higher than 700V.

[0014] Step 3: The voltage conversion module is put into operation and begins to increase the MCC bus voltage;

[0015] Step 4: If the MCC bus voltage is determined to be higher than 370V and lower than 375V, then gradient control is used to increase the MCC bus voltage; if the MCC bus voltage is determined to be higher than 375V, then the increase of the MCC bus voltage is stopped and the voltage conversion module stops working.

[0016] The second technical solution of the present invention is further characterized by:

[0017] Step 1 specifically involves: Control module A determining whether the rectifier cabinet is running. If so, control module A controls circuit breaker A to close and sends an enable signal to control module B, which then enables the voltage conversion module to enter standby mode. If not, it continues to determine whether the rectifier cabinet is running, and the voltage conversion module and circuit breaker A are not enabled.

[0018] Step 2 specifically involves the following steps: After circuit breaker A is closed and the voltage conversion module is enabled, control module B determines the MCC bus voltage by collecting the transformer primary voltage through the synchronous detection module. If the MCC bus voltage is lower than 360V and control module A determines that the DC bus voltage is higher than 700V, and both conditions are met for more than 30 seconds, then control module B controls the voltage conversion module to start working and begin to increase the MCC bus voltage.

[0019] In step 2, if control module B determines that the MCC bus voltage is higher than 360V, the voltage conversion module will not be activated; if control module A determines that the DC bus voltage is lower than 700V, the voltage conversion module will not be activated.

[0020] In step 3, control module B continues to determine the MCC bus voltage. If the MCC bus voltage is lower than 370V, the MCC bus voltage will be increased.

[0021] Step 4 specifically involves the following: If control module B determines that the MCC bus voltage is higher than 370V and lower than 375V, the voltage conversion module continues to operate and uses gradient control to increase the MCC bus voltage. This is achieved by generating adjustment curves for the MCC bus voltage and inverter current limiting through multi-point curves, so that when the MCC bus voltage is high, the voltage conversion capability is low, and when the MCC bus voltage is low, the voltage conversion capability is high. The voltage conversion capability is dynamically adjusted according to the MCC bus voltage.

[0022] The beneficial effects of this invention are:

[0023] The MCC bus voltage boosting control system of this invention for frequency conversion electric drive drilling rigs operates as follows: When the MCC bus voltage of the frequency conversion electric drive drilling rig is below 360V (i.e., the transformer primary side is below 540V) and the DC bus voltage is above 700V, and both conditions are met simultaneously for more than 30 seconds, the voltage conversion module starts working, inverting the DC power into AC power. This converted power is then supplied to the MCC bus via the transformer, boosting the MCC bus voltage from AC360V to AC370V. When the MCC bus voltage is between AC370V and AC375V, voltage gradient control is used to ensure the MCC bus voltage remains within a reasonable voltage fluctuation range. When the MCC bus voltage exceeds AC375V, the voltage conversion module stops working. This invention has been practically verified in oil drilling fields in my country, with significant results. Attached Figure Description

[0024] Figure 1 This is a simplified system diagram of the MCC bus voltage boosting control system for the variable frequency electric drive drilling rig of the present invention;

[0025] Figure 2 This is a flowchart and structural diagram of the variable frequency electric drive drilling rig MCC bus voltage boosting control method of the present invention.

[0026] In the diagram, A1 is control module A, A2 is control module B, A3 is synchronous detection module, IU is voltage conversion module, LCL is filter module, Q1 is circuit breaker A, T1 is AC600 / 400V transformer, and Q2 is circuit breaker B. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] This invention provides a variable frequency electric drive drilling rig MCC bus voltage boosting control system, such as... Figure 1 As shown, the system mainly includes control module A, control module B, synchronization detection module, voltage conversion module, filter module, circuit breaker A, transformer, and circuit breaker B. The input (DC side) of the voltage conversion module is connected to the common DC bus of the variable frequency electric drive drilling rig's electrical control system. The output (AC side) of the voltage conversion module is connected to the input of the filter module. The output of the filter module is connected to the primary side of the transformer (AC 600 / 400V) through circuit breaker A. The secondary side of the transformer is connected to the MCC bus through circuit breaker B. When the MCC bus voltage is lower than 360V (i.e., the transformer primary side is lower than 540V) and the DC bus voltage is higher than 700V, the voltage conversion module automatically starts operating. When the MCC bus voltage is higher than 375V (i.e., the transformer primary side is higher than 562V), the voltage conversion module automatically stops operating.

[0029] The present invention provides a method for controlling the MCC bus voltage boosting of a variable frequency electric drive drilling rig, such as... Figure 2 As shown, please follow these steps:

[0030] Step 1: Start. Control module A determines whether the rectifier cabinet is running. If yes, control module A controls circuit breaker A to close and sends an enable signal to control module B, which then enables the voltage conversion module to enter standby mode. If no, it continues to determine whether the rectifier cabinet is running, does not enable the voltage conversion module, and does not close circuit breaker A.

[0031] Step 2: After circuit breaker A is closed and the voltage conversion module is enabled, control module B determines the MCC bus voltage by collecting the transformer primary voltage through the synchronous detection module. If the MCC bus voltage is lower than 360V and control module A determines that the DC bus voltage is higher than 700V, and both conditions are met for more than 30 seconds, then control module B controls the voltage conversion module to start working and begin to increase the MCC bus voltage.

[0032] Step 3: If control module B determines that the MCC bus voltage is higher than 360V, the voltage conversion module will not be put into operation.

[0033] Step 4: If control module A determines that the DC bus voltage is below 700V, the voltage conversion module will not be activated.

[0034] Step 5: The voltage conversion module starts working and begins to increase the MCC bus voltage. Control module B continues to judge the MCC bus voltage. If the MCC bus voltage is lower than 370V, it continues to increase the MCC bus voltage.

[0035] Step 6: If control module B determines that the MCC bus voltage is higher than 370V but lower than 375V, the voltage conversion module continues to work and gradient control increases the MCC bus voltage. That is, by generating adjustment curves for MCC bus voltage and inverter current limiting through multi-point curves, the voltage conversion capability is low when the MCC bus voltage is high and high when the MCC bus voltage is low. The voltage conversion capability is dynamically adjusted according to the MCC bus voltage.

[0036] Step 7: If the control module B determines that the MCC bus voltage is higher than 375V, it will stop increasing the MCC bus voltage and the voltage conversion module will stop working.

[0037] Step 8. This concludes a complete MCC bus voltage boosting control process.

Claims

1. A variable frequency electric drive drilling rig MCC bus voltage boosting control system, characterized in that, Includes control module A, control module B, synchronous detection module, voltage conversion module, filtering module, circuit breaker A, transformer and circuit breaker B; The control module A is connected to the control module B via a communication cable, the voltage conversion module is connected to the control module B via a communication optical fiber, the control module B is connected to the filter module via a synchronization detection module, the input terminal of the voltage conversion module is connected to the common DC bus of the variable frequency electric drive drilling rig electrical control system, the output terminal of the voltage conversion module is connected to the input terminal of the filter module, the output terminal of the filter module is connected to the primary side of the transformer via circuit breaker A, and the secondary side of the transformer is connected to the MCC bus via circuit breaker B. The method for boosting the MCC bus voltage of a variable frequency electric drive drilling rig is implemented using a variable frequency electric drive drilling rig MCC bus voltage boosting control system, specifically following these steps: Step 1: Control module A determines whether the rectifier cabinet is running, and then controls circuit breaker A and voltage conversion module through control module A and control module B respectively; Step 2: Increase the MCC bus voltage by determining whether the MCC bus voltage is lower than 360V and the DC bus voltage is higher than 700V. Step 3: The voltage conversion module is put into operation and begins to increase the MCC bus voltage; Step 4: If the MCC bus voltage is determined to be higher than 370V and lower than 375V, then gradient control is used to increase the MCC bus voltage; if the MCC bus voltage is determined to be higher than 375V, then the increase of the MCC bus voltage is stopped and the voltage conversion module stops working. Step 2 is as follows: After circuit breaker A is closed and voltage conversion module is enabled, control module B judges the MCC bus voltage by collecting the transformer primary voltage through synchronous detection module. If the MCC bus voltage is lower than 360V and control module A judges that the DC bus voltage is higher than 700V, and both of the above conditions are met for more than 30 seconds, then control module B controls the voltage conversion module to start working and begin to increase the MCC bus voltage. In step 2, if control module B determines that the MCC bus voltage is higher than 360V, the voltage conversion module will not be activated; if control module A determines that the DC bus voltage is lower than 700V, the voltage conversion module will not be activated. In step 3, control module B continues to determine the MCC bus voltage. If the MCC bus voltage is lower than 370V, the MCC bus voltage will continue to be increased. Step 4 specifically involves: if control module B determines that the MCC bus voltage is higher than 370V and lower than 375V, the voltage conversion module continues to operate, and gradient control is used to increase the MCC bus voltage. That is, an adjustment curve for the MCC bus voltage and inverter current limit is generated through multi-point curves, so that when the MCC bus voltage is high, the voltage conversion capability is low, and when the MCC bus voltage is low, the voltage conversion capability is high. The voltage conversion capability is dynamically adjusted according to the MCC bus voltage.

2. The MCC bus voltage boosting control system for variable frequency electric drive drilling rigs according to claim 1, characterized in that, Step 1 is as follows: Control module A determines whether the rectifier cabinet is running. If so, control module A controls circuit breaker A to close and sends an enable signal to control module B, which then enables the voltage conversion module to enter standby mode. If not, it continues to determine whether the rectifier cabinet is running, and the voltage conversion module and circuit breaker A are not enabled.

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