Integrated management method of load-side power quality in variable frequency drive scenario of oil pumping unit

Abstract

The present invention discloses a method for integrated governance of power quality on the load side in the variable-frequency drive scenario of a pumping unit. The technical solution is as follows: It includes the following steps: When U1 > Uset1, the working state is defined as S1; when Uset2 < U1 < Uset1, the working states are defined as S2, S3, and S5; when U1 < Uset2, the working state is defined as S4; The integrated power quality governance device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The motor M on the load side is the pumping unit motor, which is driven by the frequency converter. The output end of the integrated power quality governance device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M. The beneficial effects are as follows: The present invention combines the characteristics of the oilfield power grid with a large number of sensitive loads and is used for the governance of voltage sags and short-term interruptions in the oilfield. It is a voltage sag governance and power grid optimization scheme that conforms to the characteristics of the oilfield power grid.

Description

Technical Field

[0001] The present invention relates to a voltage sag control and optimization technology for an oilfield power grid, and in particular to an integrated control method for load-side power quality in a pumping unit variable frequency drive scenario. Background Art

[0002] In the oil industry, compared with long-term power outages, voltage sags have the characteristics of high frequency, great harm, and difficult to detect causes. It is generally believed that 70%-80% of power quality problems are caused by voltage sags. For production lines with high continuity, if it causes the shutdown of key equipment, the entire production system may be shut down, causing incalculable losses.

[0003] The focus of traditional voltage sag control measures is to reduce the number of faults and reduce the fault time. However, the effect of voltage sag mitigation only through the power supply department is very limited. In addition, different equipment has different tolerance to voltage sags, and the exact requirements for transient power quality are also different. In recent years, people have shifted the focus of research to the development and application of control equipment to suppress voltage sags. Sensitive users can effectively reduce the adverse effects of voltage sags by installing compensation equipment. At present, the power equipment used to mitigate voltage sags mainly includes: current limiting reactors, uninterruptible power supplies (UPS), dynamic voltage restorers (DVRs), reactive power compensators (SVCs), and static synchronous compensators (STATCOMs). Voltage sag control needs to fully consider the load characteristics. For different production systems, the control methods are also diverse, and targeted research is required based on the production characteristics of the enterprise.

[0004] The Chinese patent document publication number is CN201310370105.1, and the patent name is "A voltage sag prediction and analysis method based on multi-dimensional and multi-layer association rules", which includes selecting the mining dimension of sag association rules; discretizing historical data; mining sag association rules based on minimum support and minimum confidence; constructing a knowledge base of voltage sag association rules; and matching association rules to draw prediction conclusions. The present invention mines historical voltage sag association rules, forms a knowledge base with the strong association rules obtained after mining, takes the possible future power grid operation conditions as prediction conditions, inputs them into the rule base for matching, and obtains the possible future voltage sag conditions. The present invention is a major supplement to the existing intelligent power quality monitoring system and has very important practical significance.

[0005] The Chinese patent document publication number is CN201510819753.X, and the patent name is "A method for accurately locating and optimizing voltage sag sources suitable for smart distribution networks". After a voltage sag occurs, the candidate distribution area of ​​the sag source is first determined based on the principle of sequence power increment direction. Then, the cause of the voltage sag is identified to provide targeted guidance for positioning. For voltage sags caused by short-circuit faults, within the candidate distribution area, based on the inversion idea, a short-circuit current calculation method for smart distribution networks that considers the impact of new energy access to the inverter interface is used. The fault location and transition resistance are used as optimization variables. The goal is to minimize the error between the calculated and observed values ​​of the fault current and voltage at limited observation points. A step-by-step optimization model for finding the nearest bus and the exact fault location is established, and an intelligent optimization algorithm is used to solve the problem, so as to improve positioning accuracy and achieve precise positioning.

[0006] The Chinese patent document publication number is CN201410779547.6, and the patent name is "Power quality detection method based on generalized morphological on-off and off-on wavelet transform", and the steps are: 1) Collect the signal of power quality detection and normalize it; 2) Perform the first layer of generalized morphological on-off and off-on wavelet transform processing on the normalized signal, and then extract the signal characteristics of notch and transient oscillation; 3) Perform the second layer of generalized morphological on-off and off-on wavelet transform processing on the approximate signal after the first layer of generalized morphological on-off and off-on wavelet transform processing, and then extract the signal characteristics of harmonics; 4) Perform the third layer of generalized morphological on-off and off-on wavelet transform processing on the approximate signal after the second layer of generalized morphological on-off and off-on wavelet transform processing, and then extract the signal characteristics of voltage swell, voltage sag and voltage interruption; 5) Judge the power quality according to the above-extracted signal characteristics.

[0007] Shengli Oilfield Enterprise Power Grid is large in scale, but has weak connection with the State Grid. It also includes some offshore transmission lines that supply power to offshore oil production platforms and small offshore power grids, which have their own unique characteristics. The current literature search shows that most of the existing research programs and strategies at home and abroad are aimed at suppressing and compensating for voltage sags in public power grids, but have not systematically studied the voltage sag control and optimization technology of oilfield power grids in combination with the characteristics of oilfield power grids.

[0008] Voltage sags occur frequently, cause great harm, and their causes are difficult to detect. For production lines with high continuity, if they cause shutdown of key equipment, the entire production system may be shut down, causing immeasurable losses. Summary of the invention

[0009] The purpose of the present invention is to address the above-mentioned defects in the prior art and to provide an integrated method for managing load-side power quality in a pumping unit variable frequency drive scenario, which is used to ensure the safe and stable operation of typical production equipment when the oil field power grid voltage temporarily drops or is interrupted for a short time.

[0010] An integrated power quality governance method for the load side under the variable-frequency drive scenario of a pumping unit according to the present invention has the following technical solution: It includes the following steps:

[0011] I. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the integrated power quality governance device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the integrated power quality governance device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper limit value and the lower limit value of U1 during normal system operation, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper limit value and the lower limit value of ΔU during normal system operation, and satisfy ΔU1 > 0 > ΔU2;

[0012] When U1 > Uset1, define the working state of the integrated power quality governance device as S1; when Uset2 < U1 < Uset1, define the working state of the integrated power quality governance device as S2, S3, S5; when U1 < Uset2, define the working state of the integrated power quality governance device as S4;

[0013] The integrated power quality governance device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The load-side motor M is a pumping unit motor and is driven by the frequency converter. The output end of the integrated power quality governance device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M;

[0014] II. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation when the energy storage battery of the integrated power quality governance device has not stored electricity or has insufficient electricity resulting in a small U2 when the system starts, at this time, the integrated power quality governance device operates in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality governance device through the DC / DC converter. The DC / DC converter outputs with current limiting, controls the current I to be constantly I1, and at the same time performs harmonic current compensation, in the S1 region; at this time, the integrated power quality governance device actively delays for 1 s according to the contact signal of the manual control switch K2, and then enters the detection and control function; at this time, the integrated power quality governance device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0015] Preferably, in step 2, when Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, during a certain stage of the downstroke of the pumping unit-like load, reverse power generation occurs, causing U1 to rise. At this time, the integrated power quality control device operates in state S2. The DC-link capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality control device through the DC / DC converter. The integrated power quality control device adopts the ΔU-I droop control strategy to control the magnitude and direction of the current I according to the S2 region, and at the same time compensates for harmonic currents. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0016] Preferably, in step 2, when Uset2 < U1 < Uset1 and ΔU2 < ΔU < 0, it corresponds to the situation where the pumping unit is in the upstroke and the load is heavy, resulting in a drop in the DC bus voltage of the frequency converter. At this time, the integrated power quality control device operates in state S3. The energy storage battery C2 of the integrated power quality control device charges the DC-link capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality control device adopts the ΔU-I droop control strategy to control the magnitude and direction of the current I in the S3 region. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0017] Preferably, in step 2, when U1 < Uset2 and ΔU3 < ΔU < ΔU2, it corresponds to the situation where a voltage sag occurs on the grid side, resulting in a serious drop in the DC bus voltage of the frequency converter. At this time, the integrated power quality control device operates in state S4. The energy storage battery C2 of the integrated power quality control device charges the DC-link capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality control device adopts the ΔU-I droop control strategy, actively changes the droop coefficient, and controls the magnitude and direction of the current I according to the S4 region. By increasing the current I, it plays a role in quickly supporting the DC bus voltage of the frequency converter, thereby boosting the voltage on the load side. At this time, the harmonic current compensation function is stopped.

[0018] Preferably, in step 2, when U1 > Uset1 and ΔU > ΔU1, it corresponds to the situation where reverse power generation is relatively serious during a certain stage of the downstroke of the pumping unit-like load. At this time, the integrated power quality control device operates in state S5. The DC-link capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality control device through the DC / DC converter. The DC / DC converter limits the current output and controls the current I to be constant at I1, and at the same time compensates for harmonic currents, that is, it is still in the S1 region. However, at this time, the energy-consuming resistor R is started to prevent the voltage of the DC bus of the frequency converter from being too high. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0019] Preferably, the above-mentioned integrated power quality control device is connected with the power grid, the frequency converter and the oil pump load as follows:

[0020] The inverter consists of a three-phase uncontrolled rectifier, an inverter DC side capacitor C1 and a three-phase full-bridge inverter. The three-phase electricity is connected to the three-phase uncontrolled rectifier through the load manual shutdown switch K2. The output end of the three-phase uncontrolled rectifier is connected to the inverter DC side capacitor C1. The voltage across the inverter DC side capacitor C1 is the inverter DC bus voltage U1. The two ends of the inverter DC side capacitor C1 are connected to the three-phase full-bridge inverter. The output end of the three-phase full-bridge inverter is connected to the oil pump motor M.

[0021] Preferably, the input power of the above-mentioned integrated power quality management device is provided by the inverter DC bus voltage U1, and the input end of the DC / DC converter is connected to the switching control switch K1 of the energy-consuming resistor and the external energy-consuming resistor R of the inverter DC bus, and the output end of the DC / DC converter is connected to the energy storage battery C2 and the three-phase full-bridge inverter. The voltage at both ends is the DC bus voltage U2 of the integrated power quality management device, and the output end of the three-phase full-bridge inverter is connected in parallel to the oil pump motor M.

[0022] Preferably, the output end of the above-mentioned three-phase full-bridge inverter device is connected to the oil pump motor M through the switch K3 manually locked by the integrated power quality management device.

[0023] Preferably, a controller is also provided on the outside of the integrated power quality management device, which collects the three-phase input voltage of the oil pump motor M and the auxiliary contact signal of the three-phase electricity through the load manual shutdown switch K2; controls the switching control switch K1 of the energy-consuming resistor, the switch K3 for manually locking the integrated power quality management device, the DC / DC converter and the three-phase full-bridge inverter.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The present invention has the functions of load-side harmonic control, local energy consumption, stabilization of the inverter DC bus voltage and sag control, which are as follows:

[0026] Load-side harmonic control: The integrated power quality control device detects the amplitude and phase of each harmonic current on the load side, and actively outputs a harmonic current of equal magnitude and opposite phase to achieve the control function of the load-side harmonic current;

[0027] Improve the local energy consumption capacity: store the energy generated by the reverse power generation of the pumping unit motor M locally, and release it when the DC bus voltage of the inverter is low to support the DC bus voltage of the inverter, so as to realize the recycling of energy and improve the energy utilization efficiency;

[0028] Stable control of the inverter DC bus voltage: The integrated power quality management device uses the boundary of U1 as a constraint through the DC / DC converter, adopts the ΔU-I droop control strategy, adjusts the magnitude and direction of the current I, and thus stabilizes the inverter DC bus voltage;

[0029] Load side voltage sag control function: When a voltage sag occurs on the grid side, the inverter DC bus voltage U1 will drop rapidly. The integrated power quality control device uses the boundary of U1 as a constraint through the DC / DC converter, adopts the ΔU-I droop control strategy and actively changes the droop coefficient to quickly adjust the current I, and uses C2 to store energy to support U1, ensuring the stability of the load side AC voltage.

[0030] Manual shutdown control locking function: When shutdown is required, the manual control switch K2 is disconnected, and the integrated power quality management device can receive the auxiliary contact signal of K2, thereby controlling K3 to disconnect. In this case, the DC / DC converter and the inverter link output part can be actively locked;

[0031] The present invention combines the characteristics of oilfield power grids containing a large number of sensitive loads and is used for oilfield voltage sag and short-term interruption management. It is a voltage sag management and power grid optimization solution that meets the characteristics of oilfield power grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure when the present invention is applied;

[0033] Figure 2 It is a relationship diagram between U1-Uset and the status of the integrated power quality management device;

[0034] Figure 3 It is the ΔU-I droop control curve diagram. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0036] Example 1, reference Figure 1-3 The present invention provides a method for integrated power quality management on the load side in a pumping unit variable frequency drive scenario, comprising the following steps:

[0037] 1. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the power quality integrated control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the power quality integrated control device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper limit value and the lower limit value of U1 during normal system operation, respectively, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper limit value and the lower limit value of ΔU during normal system operation, respectively, and satisfy ΔU1 > 0 > ΔU2.

[0038] When U1 > Uset1, define the working state of the power quality integrated control device as S1; when Uset2 < U1 < Uset1, define the working states of the power quality integrated control device as S2, S3, and S5; when U1 < Uset2, define the working state of the power quality integrated control device as S4.

[0039] The power quality integrated control device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The motor M on the load side is a pumping unit motor and is driven by the frequency converter. The output end of the power quality integrated control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M.

[0040] 2. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation when the energy storage battery of the power quality integrated control device has not stored electric energy or has insufficient electric energy resulting in a small U2 at the start of the system, at this time, the power quality integrated control device operates in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The DC / DC converter limits the current output and controls the current I to be constant at I1. At the same time, harmonic current compensation is carried out, and it is in the S1 region. At this time, the power quality integrated control device actively delays for 1 s according to the contact signal of the manual control switch K2, and then enters the detection and control function. At this time, the power quality integrated control device can realize the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0041] When Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, during a certain stage of the downstroke of the pumping unit - like load, reverse power generation occurs, causing U1 to rise. At this time, the integrated power quality control device operates in state S2. The DC - side capacitor C1 of the frequency converter charges the energy - storage battery C2 of the integrated power quality control device through the DC / DC converter. The integrated power quality control device adopts the ΔU - I droop control strategy, controls the magnitude and direction of the current I according to the S2 region, and simultaneously compensates for harmonic currents. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC - bus voltage of the frequency converter and harmonic governance on the load side.

[0042] When Uset2 < U1 < Uset1 and ΔU2 < ΔU < 0, corresponding to the pumping unit in the upstroke and with a heavy load, which causes the DC - bus voltage of the frequency converter to drop. At this time, the integrated power quality control device operates in state S3. The energy - storage battery C2 of the integrated power quality control device charges the DC - side capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality control device adopts the ΔU - I droop control strategy and controls the magnitude and direction of the current I in the S3 region. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC - bus voltage of the frequency converter and harmonic governance on the load side.

[0043] When U1 < Uset2 and ΔU3 < ΔU < ΔU2, corresponding to the situation where a voltage sag occurs on the grid side, resulting in a serious drop in the DC - bus voltage of the frequency converter. At this time, the integrated power quality control device operates in state S4. The energy - storage battery C2 of the integrated power quality control device charges the DC - side capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality control device adopts the ΔU - I droop control strategy, actively changes the droop coefficient, and controls the magnitude and direction of the current I according to the S4 region. By increasing the current I, it plays a role in quickly supporting the DC - bus voltage of the frequency converter, thereby increasing the load - side voltage. At this time, the harmonic - current compensation function is stopped.

[0044] When U1 > Uset1 and ΔU > ΔU1, corresponding to a relatively serious reverse power generation during a certain stage of the downstroke of the pumping unit - like load. At this time, the integrated power quality control device operates in state S5. The DC - side capacitor C1 of the frequency converter charges the energy - storage battery C2 of the integrated power quality control device through the DC / DC converter. The DC / DC converter limits the current output, controls the current I to be constant at I1, and simultaneously compensates for harmonic currents, that is, it is still in the S1 region. However, at this time, the energy - consuming resistor R is started to prevent the voltage of the DC - bus of the frequency converter from being too high. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC - bus voltage of the frequency converter and harmonic governance on the load side.

[0045] Refer to Figure 1 , the connection of the integrated power quality control device with the power grid, frequency converter, and pumping unit load is as follows:

[0046] The inverter consists of a three-phase uncontrolled rectifier, an inverter DC side capacitor C1 and a three-phase full-bridge inverter. The three-phase electricity is connected to the three-phase uncontrolled rectifier through the load manual shutdown switch K2. The output end of the three-phase uncontrolled rectifier is connected to the inverter DC side capacitor C1. The voltage across the inverter DC side capacitor C1 is the inverter DC bus voltage U1. The two ends of the inverter DC side capacitor C1 are connected to the three-phase full-bridge inverter. The output end of the three-phase full-bridge inverter is connected to the oil pump motor M.

[0047] The input power of the above-mentioned integrated power quality management device is provided by the inverter DC bus voltage U1, and the input end of the DC / DC converter is connected to the switching control switch K1 of the energy-consuming resistor and the external energy-consuming resistor R of the inverter DC bus. The output end of the DC / DC converter is connected to the energy storage battery C2 and the three-phase full-bridge inverter. The voltage at both ends is the DC bus voltage U2 of the integrated power quality management device, and the output end of the three-phase full-bridge inverter is connected in parallel to the oil pump motor M.

[0048] The output end of the above-mentioned three-phase full-bridge inverter device is connected to the pumping unit motor M through the switch K3 which is manually locked by the integrated power quality management device.

[0049] Embodiment 2, a method for integrated management of load-side power quality in a pumping unit variable frequency drive scenario mentioned in the present invention,

[0050] A controller is also provided on the outside of the integrated power quality management device. The controller collects the three-phase input voltage of the oil pump motor M and the auxiliary contact signal of the three-phase power through the load manual shutdown switch K2; controls the switching control switch K1 output to the energy-consuming resistor, the switch K3 for manually locking the integrated power quality management device, the DC / DC converter and the three-phase full-bridge inverter.

[0051] It should be noted that the circuit of the controller is a conventional technology well known to those skilled in the art, and therefore, the detailed circuit is not described again.

[0052] Embodiment 3, a method for integrated management of load-side power quality in a pumping unit variable frequency drive scenario mentioned in the present invention, comprises the following steps:

[0053] 1. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the integrated power quality control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the integrated power quality control device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper and lower limit values of U1 during normal system operation, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper and lower limit values of ΔU during normal system operation, and satisfy ΔU1 > 0 > ΔU2.

[0054] When U1 > Uset1, define the working state of the integrated power quality control device as S1; when Uset2 < U1 < Uset1, define the working states of the integrated power quality control device as S2, S3, S5; when U1 < Uset2, define the working state of the integrated power quality control device as S4.

[0055] The integrated power quality control device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The motor M on the load side is a pumping unit motor, which is driven by the frequency converter. The output end of the integrated power quality control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M.

[0056] 2. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation when the energy storage battery of the integrated power quality control device has not stored electricity or has insufficient electricity, resulting in a small U2 when the system starts. At this time, the integrated power quality control device works in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality control device through the DC / DC converter. The DC / DC converter outputs with current limiting, controls the current I to be constantly I1, and at the same time performs harmonic current compensation, in the S1 region; at this time, the integrated power quality control device actively delays for 1S according to the contact signal of the manual control switch K2, and then enters the detection control function; at this time, the integrated power quality control device can realize the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0057] Example 4, a method for integrated power quality control on the load side in a variable-frequency drive scenario of a pumping unit, includes the following steps:

[0058] 1. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the power quality integrated control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the power quality integrated control device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper limit and lower limit of U1 during normal system operation, respectively, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper limit and lower limit of ΔU during normal system operation, respectively, and satisfy ΔU1 > 0 > ΔU2.

[0059] When U1 > Uset1, define the working state of the power quality integrated control device as S1; when Uset2 < U1 < Uset1, define the working states of the power quality integrated control device as S2, S3, S5; when U1 < Uset2, define the working state of the power quality integrated control device as S4.

[0060] The power quality integrated control device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The motor M on the load side is a pumping unit motor, which is driven by the frequency converter. The output end of the power quality integrated control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M.

[0061] 2. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation when the energy storage battery of the power quality integrated control device has no stored electricity or insufficient electricity resulting in a small U2 at the start of the system, at this time, the power quality integrated control device operates in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The DC / DC converter limits the current output and controls the current I to be constant at I1, and at the same time, harmonic current compensation is carried out, in the S1 region; at this time, the power quality integrated control device actively delays for 1 s according to the contact signal of the manual control switch K2, and then enters the detection and control function; at this time, the power quality integrated control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic control on the load side.

[0062] When Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, during a certain stage of the downstroke of the pumping unit - type load, reverse power generation occurs, causing U1 to rise. At this time, the integrated power quality control device operates in state S2. The DC - side capacitor C1 of the frequency converter charges the energy - storage battery C2 of the integrated power quality control device through the DC / DC converter. The integrated power quality control device adopts a ΔU - I droop control strategy to control the magnitude and direction of the current I according to the S2 region and simultaneously compensates for harmonic currents. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0063] Embodiment 5. A method for integrated power quality control on the load side in a variable - frequency drive scenario of a pumping unit according to the present invention includes the following steps:

[0064] I. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the integrated power quality control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the integrated power quality control device, and its magnitude and direction can be controlled by the DC / DC converter; Define Uset1 and Uset2 as the upper and lower limits of U1 during normal system operation, respectively, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper and lower limits of ΔU during normal system operation, respectively, and satisfy ΔU1 > 0 > ΔU2;

[0065] When U1 > Uset1, define the working state of the integrated power quality control device as S1; when Uset2 < U1 < Uset1, define the working states of the integrated power quality control device as S2, S3, S5; when U1 < Uset2, define the working state of the integrated power quality control device as S4;

[0066] The integrated power quality control device includes a DC / DC converter, an energy - storage battery C2, and a three - phase full - bridge inverter device. The energy - storage battery C2 is connected to the DC - side capacitor C1 of the frequency converter and the energy - consuming resistor R through the DC / DC converter. The load - side motor M is a pumping unit motor and is driven by the frequency converter. The output end of the integrated power quality control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M;

[0067] II. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation where when the power quality integrated control device starts up, the energy storage battery of the power quality integrated control device does not store electric energy or has insufficient electric energy resulting in a small U2. At this time, the power quality integrated control device operates in the S1 state. The DC-link capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The DC / DC converter limits the output current, and the control current I is kept constant at I1. At the same time, harmonic current compensation is carried out, and it is in the S1 region. At this time, the power quality integrated control device actively delays for 1 s according to the contact signal of the manual control switch K2, and then enters the detection and control function. At this time, the power quality integrated control device can realize the functions of stabilizing the DC bus voltage of the frequency converter and harmonic治理 of the load side.

[0068] When Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, corresponding to the situation where during a certain stage of the downstroke of a pumping unit-like load, reverse power generation causes U1 to rise. At this time, the power quality integrated control device operates in the S2 state. The DC-link capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The power quality integrated control device adopts the ΔU-I droop control strategy to control the magnitude and direction of the current I according to the S2 region. At the same time, harmonic current compensation is carried out. At this time, the power quality integrated control device can realize the functions of stabilizing the DC bus voltage of the frequency converter and harmonic治理 of the load side.

[0069] When Uset2 < U1 < Uset1 and ΔU2 < ΔU < 0, corresponding to the situation where the pumping unit is in the upstroke and the load is heavy, resulting in a drop in the DC bus voltage of the frequency converter. At this time, the power quality integrated control device operates in the S3 state. The energy storage battery C2 of the power quality integrated control device charges the DC-link capacitor C1 of the frequency converter through the DC / DC converter. The power quality integrated control device adopts the ΔU-I droop control strategy to control the magnitude and direction of the current I in the S3 region. At this time, the power quality integrated control device can realize the functions of stabilizing the DC bus voltage of the frequency converter and harmonic治理 of the load side.

[0070] Embodiment 6. A method for integrated power quality治理 on the load side in a variable-frequency drive scenario of a pumping unit according to the present invention includes the following steps:

[0071] 1. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the power quality integrated control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the power quality integrated control device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper limit and lower limit of U1 during normal system operation, respectively, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper limit and lower limit of ΔU during normal system operation, respectively, and satisfy ΔU1 > 0 > ΔU2.

[0072] When U1 > Uset1, define the working state of the power quality integrated control device as S1; when Uset2 < U1 < Uset1, define the working states of the power quality integrated control device as S2, S3, and S5; when U1 < Uset2, define the working state of the power quality integrated control device as S4.

[0073] The power quality integrated control device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The motor M on the load side is a pumping unit motor, which is driven by the frequency converter. The output end of the power quality integrated control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M.

[0074] 2. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation when the energy storage battery of the power quality integrated control device has no stored electrical energy or insufficient electrical energy resulting in a small U2 at the start of the system, at this time, the power quality integrated control device operates in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The DC / DC converter limits the output current and controls the current I to be constantly I1, and at the same time performs harmonic current compensation, in the S1 region; at this time, the power quality integrated control device actively delays for 1 s according to the contact signal of the manual control switch K2, and then enters the detection and control function; at this time, the power quality integrated control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic control on the load side.

[0075] When Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, during a certain stage of the downstroke of the pumping unit-like load, reverse power generation occurs, causing U1 to rise. At this time, the integrated power quality control device operates in state S2. The DC-side capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality control device through the DC / DC converter. The integrated power quality control device adopts the ΔU-I droop control strategy, controls the magnitude and direction of the current I according to the S2 region, and simultaneously compensates for harmonic currents. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0076] When Uset2 < U1 < Uset1 and ΔU2 < ΔU < 0, it corresponds to the situation where the pumping unit is in the upstroke and the load is heavy, resulting in a decrease in the DC bus voltage of the frequency converter. At this time, the integrated power quality control device operates in state S3. The energy storage battery C2 of the integrated power quality control device charges the DC-side capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality control device adopts the ΔU-I droop control strategy and controls the magnitude and direction of the current I in the S3 region. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0077] When U1 > Uset1 and ΔU > ΔU1, it corresponds to a situation where reverse power generation is relatively serious during a certain stage of the downstroke of the pumping unit-like load. At this time, the integrated power quality control device operates in state S5. The DC-side capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality control device through the DC / DC converter. The DC / DC converter limits the current output and controls the current I to be constantly I1, and simultaneously compensates for harmonic currents, that is, it is still in the S1 region. However, at this time, the energy-consuming resistor R is started to prevent the voltage of the DC bus of the frequency converter from being too high. At this time, the integrated power quality control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

[0078] As described above, it is only some preferred embodiments of the present invention. Any person skilled in the art may modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modification or equivalent replacement made according to the technical solutions of the present invention falls within the scope of protection required by the present invention.

Claims

1. A method for integrated management of load-side power quality in a pumping unit variable frequency drive scenario, characterized by: It includes the following steps:

1. Define ΔU as the voltage difference between the DC bus voltage U1 of the frequency converter and the DC bus voltage U2 of the power quality integrated control device, and the expression is ΔU = U1 - U2; I is the current flowing from the DC bus of the frequency converter to the power quality integrated control device, and its magnitude and direction can be controlled by the DC / DC converter; define Uset1 and Uset2 as the upper limit value and the lower limit value of U1 during normal system operation, and satisfy Uset1 > Uset2 > 0; ΔU1 and ΔU2 are the upper limit value and the lower limit value of ΔU during normal system operation, and satisfy ΔU1 > 0 > ΔU2; When U1 > Uset1, define the working state of the power quality integrated control device as S1; when Uset2 < U1 < Uset1, define the working states of the power quality integrated control device as S2, S3, and S5; When U1 < Uset2, define the working state of the power quality integrated control device as S4; The power quality integrated control device includes a DC / DC converter, an energy storage battery C2, and a three-phase full-bridge inverter device. The energy storage battery C2 is connected to the DC side capacitor C1 of the frequency converter and the energy-consuming resistor R through the DC / DC converter. The load-side motor M is a pumping unit motor and is driven by the frequency converter. The output end of the power quality integrated control device is connected in parallel with the output end of the frequency converter to jointly supply power to the pumping unit motor M; 2. When Uset2 < U1 < Uset1 and ΔU > ΔU1, corresponding to the situation where the energy storage battery of the power quality integrated control device has no stored electrical energy or insufficient electrical energy when the system starts, at this time, the power quality integrated control device works in the S1 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The DC / DC converter outputs with current limiting, controls the current I to be constantly I1, and at the same time performs harmonic current compensation, in the S1 region; at this time, the power quality integrated control device actively delays for 1S according to the contact signal of the manual control switch K2, and then enters the detection and control function; at this time, the power quality integrated control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side; When Uset2 < U1 < Uset1 and 0 < ΔU < ΔU1, corresponding to the situation where U1 rises due to reverse power generation during a certain stage of the downstroke of a pumping unit-like load, at this time, the power quality integrated control device works in the S2 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the power quality integrated control device through the DC / DC converter. The power quality integrated control device adopts a ΔU-I droop control strategy to control the magnitude and direction of the current I according to the S2 region, and at the same time performs harmonic current compensation; at this time, the power quality integrated control device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side; When Uset2 < U1 < Uset1 and ΔU2 < ΔU < 0, it corresponds to the situation that the pumping unit is in the upstroke and the load is heavy, resulting in the decrease of the DC bus voltage of the frequency converter. At this time, the integrated power quality management device works in the S3 state. The energy storage battery C2 of the integrated power quality management device charges the DC side capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality management device adopts the ΔU-I droop control strategy to control the magnitude and direction of the current I in the S3 region. At this time, the integrated power quality management device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side. When U1 < Uset2 and ΔU3 < ΔU < ΔU2, it corresponds to the situation that the voltage sag on the grid side causes a serious drop in the DC bus voltage of the frequency converter. At this time, the integrated power quality management device works in the S4 state. The energy storage battery C2 of the integrated power quality management device charges the DC side capacitor C1 of the frequency converter through the DC / DC converter. The integrated power quality management device adopts the ΔU-I droop control strategy, actively changes the droop coefficient and controls the magnitude and direction of the current I according to the S4 region. By increasing the current I, it plays a role in quickly supporting the DC bus voltage of the frequency converter, thereby improving the voltage on the load side. At this time, the harmonic current compensation function is stopped. When U1 > Uset1 and ΔU > ΔU1, it corresponds to the situation that the reverse power generation is relatively serious in a certain stage of the downstroke of the pumping unit type load. At this time, the integrated power quality management device works in the S5 state. The DC side capacitor C1 of the frequency converter charges the energy storage battery C2 of the integrated power quality management device through the DC / DC converter. The DC / DC converter limits the current output and controls the current I to be constant at I1. At the same time, harmonic current compensation is carried out, that is, it is still in the S1 region. But at this time, the energy-consuming resistor R is started to prevent the voltage of the DC bus of the frequency converter from being too high. At this time, the integrated power quality management device can achieve the functions of stabilizing the DC bus voltage of the frequency converter and harmonic governance on the load side.

2. The integrated power quality management method on the load side in the variable frequency drive scenario of the oil pump according to claim 1 is characterized by: The connection of the described integrated power quality management device with the power grid, frequency converter and pumping unit load is as follows: The frequency converter consists of a three-phase uncontrolled rectifier device, a DC side capacitor C1 of the frequency converter and a three-phase full-bridge inverter device. The three-phase power is connected to the three-phase uncontrolled rectifier device through the load manual shutdown switch K2. The output end of the three-phase uncontrolled rectifier device is connected to the DC side capacitor C1 of the frequency converter. The voltage across the two ends of the DC side capacitor C1 of the frequency converter is the DC bus voltage U1 of the frequency converter. The two ends of the DC side capacitor C1 of the frequency converter are connected to the three-phase full-bridge inverter device. The output end of the three-phase full-bridge inverter device is connected to the pumping unit motor M.

3. The integrated power quality management method on the load side in the variable frequency drive scenario of the oil pump according to claim 1 or 2 is characterized in that: The input power supply of the described integrated power quality management device is provided by the DC bus voltage U1 of the frequency converter. And the input end of the DC / DC converter is connected to the switching control switch K1 of the energy-consuming resistor and the externally connected energy-consuming resistor R of the DC bus of the frequency converter. The output end of the DC / DC converter is connected to the energy storage battery C2 and the three-phase full-bridge inverter device. The voltage across the two ends is the DC bus voltage U2 of the integrated power quality management device. The output end of the three-phase full-bridge inverter device is connected in parallel to the pumping unit motor M.

4. The integrated power quality management method for the load side in the variable frequency drive scenario of the oil pump according to claim 3 is characterized by: The output end of the three-phase full-bridge inverter device is connected to the pumping unit motor M through the switch K3 manually locked by the integrated power quality management device.

5. The integrated power quality management method on the load side in the variable frequency drive scenario of the oil pump according to claim 3 is characterized by: A controller is also provided on the outside of the integrated power quality management device. The controller collects the three-phase input voltage of the oil pump motor M and the auxiliary contact signal of the three-phase power through the load manual shutdown switch K2; controls the switching control switch K1 of the energy-consuming resistor, the switch K3 for manually locking the integrated power quality management device, the DC / DC converter and the three-phase full-bridge inverter.

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