High-voltage brushless doubly-fed motor control method and device

Abstract

The invention discloses a high-voltage brushless doubly-fed motor control method, system and device, and the method comprises the steps: collecting the load current of a doubly-fed motor, reducing the active power of a stator of the doubly-fed motor if the load current exceeds a load current limit value, then reducing the active power of the stator until the load current is smaller than the load current limit value, and enabling the output of the doubly-fed motor to be normal, according to the doubly-fed motor protection method, device and system provided by the invention, when the doubly-fed motor has the overcurrent fault, the stator active power of the doubly-fed motor is adjusted, so that the stator active power of the motor is effectively reduced, the rotating speed of the motor is reduced, and finally, the purpose of protecting the motor is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and in particular relates to a control method, system and device for a high-voltage brushless double-fed motor. Background Art

[0002] Doubly-fed motors have the advantages of high power factor, high efficiency, wide voltage range, flexible control and low cost, and can meet the application requirements of wind power generation, industrial traction, water conservancy and electricity, and seafood farming. They are most widely used in my country. There are many types of failures in doubly-fed motors. In actual use, the two most common failures encountered by users are doubly-fed motors with no output and excessive starting impact. Both of these failures will cause production interruptions for users, and in serious cases will cause great economic losses.

[0003] In the case of a stalled and non-output fault, a large part of the current will be useless and useless loss, the motor basically does not output power, and the motor speed remains at zero. If the motor power is adjusted according to the actual load, the speed cannot be adjusted, and the load requirements cannot be met. As for the starting impact fault, it is because the internal inverter of the doubly fed motor will produce current imbalance during startup, causing the starting impact current to be too large. When the current is too large, due to the internal temperature rise of the stator winding, it may cause the line to overcurrent or cause the stator winding insulation to age faster, resulting in damage to the motor winding. For the above two faults, the commonly used protection schemes are as follows:

[0004] 1. Detect overcurrent protection: When the current reaches the set value, overcurrent protection is performed. This solution can only be disconnected by a switch and cannot solve the fault problem.

[0005] 2. No output for stalled rotor: By detecting the size of the stator current, if the current does not decay within a certain period of time, it is considered that the motor is stalled and the motor is started and dragged. This solution requires manual switch control, which may easily cause production interruption for users.

[0006] 3. No output for stalled rotor: The speed of the stator motor is determined by detecting the position sensor. When the motor speed is lower than a certain value, the motor is considered to be stalled and the motor is started. This solution interferes with the detection principle of the position sensor and cannot determine the fault of the sensor itself.

[0007] 4. No output for stalled rotor: The motor speed is determined by detecting the stator current. When the load current is large, the motor is considered to be stalled and the motor is started and dragged. This solution has low accuracy in current detection, which makes the protection action prone to false operation.

[0008] Therefore, at present, there is a lack of a method to solve the problems of no output due to stalling of the doubly-fed motor and excessive starting impact, so as to improve the stability and initiative of the control. Summary of the invention

[0009] In view of the above technical problems, the present application proposes a high-voltage brushless double-fed motor control method, system and device system. The specific technical solutions are as follows:

[0010] In a first aspect, the present invention provides a high-voltage brushless double-fed motor control method, comprising:

[0011] Collect the load current of the doubly-fed generator;

[0012] If the load current exceeds the load current limit, reducing the stator active power of the doubly-fed generator;

[0013] The stator active power is reduced until the load current is less than the load current limit and the output of the double-fed motor is normal.

[0014] Furthermore, if the load current exceeds the load current limit, reducing the stator power of the doubly-fed motor is specifically:

[0015] According to a preset priority mode, reducing the stator power of the doubly-fed motor, the priority mode being divided into a grid-connected inversion priority and a load inversion priority;

[0016] If the doubly-fed motor is in the grid-connected inversion priority, the stator power of the doubly-fed motor is reduced, specifically: a first variable is set to 1, and the size between the load current and the load current limit is determined, wherein the first variable is a constant and is greater than 0;

[0017] If the load current is greater than the load current limit, reducing the stator active power by a first preset value;

[0018] The magnitude between the load current and the load current limit is determined; if the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0019] Furthermore, if the doubly-fed motor is in a grid-connected inversion priority, reducing the stator power of the doubly-fed motor also includes:

[0020] If the load current is less than or equal to the load current limit, the first variable is set to the difference between the first variable and the first preset value, and the first variable is divided by the first preset value to obtain a third variable. If the third variable is greater than or equal to 1, the stator active power is increased by the first preset value.

[0021] Furthermore, reducing the stator power under the grid-connected inverter priority also includes:

[0022] If the load current is less than or equal to the load current limit, the load inversion priority is entered, and the stator power is reduced under the load inversion priority, which specifically includes: setting the second variable to 1;

[0023] Determining the magnitude between the load current and the load current limit;

[0024] The judgment result is that if the load current is greater than the load current limit, the size between the stator power and the rated power is judged, wherein the second variable is a constant and is greater than 0;

[0025] If the stator power is greater than the rated power, the stator power is reduced by a second preset value.

[0026] Further, determining to reduce the stator power under the load inversion priority also includes:

[0027] If the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0028] Further, determining to reduce the stator power under the load inversion priority also includes:

[0029] If the load current is less than or equal to the load current limit, the second variable is set to the difference between the second variable and the second preset value, the second variable is divided by the second preset value, and if the second variable is greater than or equal to 1, the stator power is increased by a second preset value.

[0030] In a second aspect, the present invention provides a doubly-fed electric machine control device, the device comprising:

[0031] An acquisition module is used to collect the load current of the double-fed generator;

[0032] A processing module, configured to reduce the stator active power of the double-fed generator if the load current exceeds the load current limit;

[0033] The stator active power is reduced until the load current is less than the load current limit and the output of the double-fed motor is normal.

[0034] Furthermore, if the load current exceeds the load current limit, reducing the stator power of the doubly-fed motor is specifically as follows:

[0035] According to a preset priority mode, reducing the stator power of the doubly-fed motor, the priority mode being divided into a grid-connected inversion priority and a load inversion priority;

[0036] If the doubly-fed motor is in the grid-connected inversion priority, the stator power of the doubly-fed motor is reduced, specifically: a first variable is set to 1, and the size between the load current and the load current limit is determined, wherein the first variable is a constant and is greater than 0;

[0037] If the load current is greater than the load current limit, reducing the stator active power by a first preset value;

[0038] The magnitude between the load current and the load current limit is determined; if the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0039] Furthermore, if the doubly-fed motor is in a grid-connected inversion priority, reducing the stator power of the doubly-fed motor also includes:

[0040] If the load current is less than or equal to the load current limit, the first variable is set to the difference between the first variable and the first preset value, and the first variable is divided by the first preset value to obtain a third variable. If the third variable is greater than or equal to 1, the stator active power is increased by the first preset value.

[0041] Furthermore, reducing the stator power under the grid-connected inverter priority also includes:

[0042] If the load current is less than or equal to the load current limit, the load inversion priority is entered, and the stator power is reduced under the load inversion priority, which specifically includes: setting the second variable to 1;

[0043] Determining the magnitude between the load current and the load current limit;

[0044] If the load current is greater than the load current limit, determine the magnitude between the stator power and the rated power, wherein the second variable is a constant and is greater than 0;

[0045] If the stator power is greater than the rated power, the stator power is reduced by a second preset value.

[0046] Further, determining to reduce the stator power under the load inversion priority also includes:

[0047] If the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0048] Further, determining to reduce the stator power under the load inversion priority also includes:

[0049] If the load current is less than or equal to the load current limit, the second variable is set to the difference between the second variable and the second preset value, the second variable is divided by the second preset value to obtain the fourth variable, and if the fourth variable is greater than or equal to 1, the stator power is increased by the second preset value.

[0050] In a third aspect, the present invention provides a doubly-fed electric machine control system, the system comprising:

[0051] A collection unit, used for collecting the load current of the double-fed generator;

[0052] A storage unit, used for storing a load current limit value;

[0053] A processing unit, configured to reduce the stator active power of the double-fed motor if the load current exceeds the load current limit;

[0054] The stator active power is reduced until the load current is less than the load current limit and the output of the double-fed motor is normal.

[0055] Furthermore, the processing unit is used to reduce the stator power of the double-fed motor if the load current exceeds the load current limit value by:

[0056] According to a preset priority mode, reducing the stator power of the doubly-fed motor, the priority mode being divided into a grid-connected inversion priority and a load inversion priority;

[0057] If the doubly-fed motor is in the grid-connected inversion priority, the stator power of the doubly-fed motor is reduced, specifically: a first variable is set to 1, and the size between the load current and the load current limit is determined, wherein the first variable is a constant and is greater than 0;

[0058] If the load current is greater than the load current limit, reducing the stator active power by a first preset value;

[0059] The magnitude between the load current and the load current limit is determined; if the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0060] Further, the processing unit is further configured to reduce the stator power of the doubly-fed motor if the doubly-fed motor is in a grid-connected inversion priority, and further includes:

[0061] If the load current is less than or equal to the load current limit, the first variable is set to the difference between the first variable and the first preset value, and the first variable is divided by the first preset value to obtain a third variable. If the third variable is greater than or equal to 1, the stator active power is increased by the first preset value.

[0062] Furthermore, the processing unit is further used to determine whether to reduce the stator power under the grid-connected inverter priority, and further includes:

[0063] If the load current is less than or equal to the load current limit, the load inversion priority is entered, and the stator power is reduced under the load inversion priority, which specifically includes: setting the second variable to 1;

[0064] Determining the magnitude between the load current and the load current limit;

[0065] If the load current is greater than the load current limit, determine the magnitude between the stator power and the rated power, wherein the second variable is a constant and is greater than 0;

[0066] If the stator power is greater than the rated power, the stator power is reduced by a second preset value.

[0067] Further, the processing unit is used to determine whether to reduce the stator power under the load inversion priority, and further includes:

[0068] If the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

[0069] Further, the processing unit is used to determine whether to reduce the stator power under the load inversion priority, and further includes:

[0070] If the load current is less than or equal to the load current limit, the second variable is set to the difference between the second variable and the second preset value, the second variable is divided by the second preset value to obtain the fourth variable, and if the fourth variable is greater than or equal to 1, the stator power is increased by the second preset value.

[0071] The beneficial effects of the present invention are:

[0072] (1) By collecting the load current of the doubly-fed motor in real time and detecting the load current, when the load current of the doubly-fed motor is too large and exceeds the stator current limit value, the stator active power is actively adjusted to reduce the current on the stator side of the motor, thereby reducing the load current and avoiding the occurrence of stator overcurrent faults;

[0073] (2) Through the preset priority mode, the stator active power can be controlled more reasonably and the grid-connected inverter requirements can be met first, making the application range of the doubly-fed generator wider;

[0074] (3) Through the preset priority mode, the stator active power can be controlled more reasonably, and the load demand can be met first, which can better protect the doubly fed generator. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0076] Example

[0077] This embodiment provides a high-voltage brushless doubly-fed motor control method, the doubly-fed motor includes two inverters, the first inverter is a grid-side controllable inverter, and the second inverter is a load-side controllable inverter. The control method includes the following steps:

[0078] S1. Collect the load current of the doubly-fed motor. The grid-side inverter is connected to the doubly-fed motor through the grid-side DC bus. The three-phase AC power output by the grid-side inverter is input into the doubly-fed motor. The load-side inverter is connected to the doubly-fed motor through the load-side DC bus. The three-phase AC power output by the load-side inverter is also input into the doubly-fed motor. The mechanical energy in the doubly-fed motor is converted into DC power on the load side by the load-side inverter for storage.

[0079] S2. Determine the size of the load current and the load current limit. When the load current exceeds the load current limit, reduce the stator active power of the doubly-fed motor until the load current is less than the load current limit.

[0080] There are many ways to reduce the stator active power of the doubly-fed generator, such as by changing the output parameters of the grid-side inverter or the output parameters of the load-side inverter.

[0081] The following is a detailed description of reducing the stator active power:

[0082] The stator power of the doubly-fed motor is reduced according to a preset priority level mode, wherein the priority mode is divided into a grid-connected inversion priority mode and a load inversion priority mode.

[0083] If the doubly-fed generator is in the grid-connected inverter priority, execute:

[0084] Set the first variable. The first variable is a constant greater than 0. The default value is 1.

[0085] Determine the magnitude between the load current and the load current limit, if the load current is greater than the load current limit, reduce the stator active power by a first preset value, the first preset value being a constant greater than 0;

[0086] The judgment operation is executed cyclically until the load current is no longer greater than the load current limit.

[0087] If the doubly-fed generator is in the grid-connected inverter priority, the following is also executed:

[0088] Determine the size between the load current and the load current limit. If the load current is less than or equal to the load current limit, set the first variable to the difference between the first variable and the first preset value, and divide the first variable by the first preset value to obtain the third variable.

[0089] Determine whether the third variable is greater than or equal to 1, and if so, increase the stator active power by a first preset value.

[0090] Furthermore, if the doubly-fed generator is in the grid-connected inverter priority, reducing the stator power also includes:

[0091] Determine the size between the load current and the load current limit. If the load current is less than or equal to the load current limit, enter the load inversion priority. The stator power is reduced under the load inversion priority, including:

[0092] Set the second variable. The second variable is a constant greater than 0. The default value is 1.

[0093] Determine the size between the load current and the load current limit. If the load current is greater than the load current limit, then determine the size between the stator power and the rated power. If the stator power is greater than the rated power, reduce the stator power by a second preset value.

[0094] When the doubly-fed generator is under load inversion priority, reducing the stator power also includes:

[0095] The magnitude of the load current and the load current limit is determined. If the load current is greater than the load current limit, the operation of reducing the stator active power is repeatedly performed.

[0096] The doubly-fed machine is under load inversion priority, and the stator power reduction also includes

[0097] Determine the magnitude of the load current and the load current limit, if the load current is less than or equal to the load current limit, set the second variable to the difference between the second variable and the second preset value, and divide the second variable by the second preset value to obtain a fourth variable;

[0098] Determine the magnitude of the fourth variable and 1, and then increase the stator power by a second preset value.

[0099] The settings of the first preset value and the second preset value are related to the load current limit value. The larger the load current limit value is, the larger the first preset value and the second preset value are.

[0100] In the above steps, since the system needs to quickly establish the initialized grid voltage and frequency when the doubly-fed generator is started, the grid-side inverter first enters the operating state, and the load-side inverter is in the standby state. The priority of the load inversion is slightly lower than that of the grid side. The first preset value and the second preset value can be set to be slightly higher than the load current limit.

[0101] During operation, the system reaches a steady state, and the grid-side inverter and the load inverter both enter the operation mode. If the load current is greater than the preset load current limit and the stator power is greater than the rated power, the output power of both the grid side and the load side is reduced at the same time.

[0102] During operation, if the load current is greater than the preset load current limit but does not exceed the first preset value, the first variable remains unchanged and the stator active power is set unchanged; if the load current is less than or equal to the load current limit, the first variable is set to the difference between the first variable and the first preset value, and the third variable is calculated. The third variable is set to the difference between the first variable and the first preset value divided by the first preset value. If the third variable is greater than or equal to 1, the stator active power is increased by the first preset value.

[0103] If the load current is greater than the load current limit but does not exceed the second preset value, the second variable remains unchanged and the stator active power is set unchanged; if the load current is less than or equal to the load current limit, the second variable is set to the difference between the second variable and the second preset value, and the fourth variable is calculated. The fourth variable is set to the ratio of the difference between the second variable and the second preset value to the second preset value. If the fourth variable is greater than or equal to 1, the stator active power is increased by the second preset value.

[0104] In steady-state operation, the load current is not less than the load current limit. When the load current is greater than the load current limit, the stator active power is reduced. When the load current is less than or equal to the load current limit, the variable is calculated. If the variable is greater than or equal to 1, the stator active power is increased. While increasing the stator active power, the stator reactive power is reduced.

[0105] In steady state operation, the load current is less than the load current limit and the set sub-active power remains unchanged.

[0106] During operation, when a fault occurs on the grid side, the double-fed motor starts the grid-side inverter and reduces the stator active power. When the load current is greater than the load current limit, the stator active power is reduced. When the load current is less than or equal to the load current limit, the variable is calculated. If the variable is greater than or equal to 1, the stator active power is increased. While increasing the active power, the stator reactive power is reduced. When the load current is greater than the load current limit, if the stator active power is greater than the rated power, the stator active value of the double-fed motor is reduced, and the stator active power is reduced to between the stator active power and the rated power. The variable is calculated again. If the variable is greater than or equal to 1, the stator active power is increased by a second preset value.

[0107] During operation, when a fault occurs on the load side, the doubly-fed generator starts the load-side inverter, and when the load current is greater than the load current limit, the load current is reduced.

[0108] When a fault occurs on the grid side, the grid-side inverter control voltage drops to 0V, the grid-side output power drops to 0, the load current increases, and if it is greater than the load current limit, the stator active power is reduced.

[0109] When a fault occurs on the load side, the load side inverter stops working. At this time, the load current is greater than the load current limit. However, since the grid-side inverter continues to work, the stator active power and stator reactive power are both maintained at the rated power. When the load current is less than the load current limit, the stator active power and stator reactive power are adjusted to maintain the output load current limit.

[0110] When a fault occurs on the grid side, the grid-side inverter is derated, the load current increases, and the load current is greater than the load current limit. The stator active power is reduced until the load current is less than the load current limit. After the grid-side inverter is derated, the stator active power is set to remain unchanged.

[0111] When the grid-side inverter outputs normally, the load current is not less than the load current limit. The sub-active power is set and the sub-reactive power is set to be adjusted at the same time, wherein the adjustment of the sub-active power is calculated based on the load current and the first preset value, specifically: the load current minus the load current limit divided by the first preset value, and the sub-active power remains unchanged; when the load current is less than the load current limit, the sub-active power is set to the rated power.

[0112] The adjustment of the sub-reactive power is set according to the load current and the load current limit. Specifically, the difference between the sub-reactive power and the load current limit is divided by the load current limit. When the load current is less than the load current limit, the sub-active power is set, and the power of the sub-reactive power is set to the rated power.

[0113] When a fault occurs on the load side, the load side inverter stops working, the load current is greater than the load current limit, and the stator active power is reduced until the load current value is less than the load current limit, and the load current limit is greater than or equal to the fault current value. When the load side inverter resumes working, if the load current is greater than the load current limit, the active power is reduced until the load current is less than the load current limit.

[0114] In the embodiment, the stator active power, stator reactive power and load current in the doubly-fed motor are associated, and the stator active power and stator reactive power are adjusted according to the load current, thereby protecting the stable operation of the doubly-fed motor. The priority of adjusting the active and reactive outputs can be adjusted according to the importance of the doubly-fed motor protection to ensure the stable operation of the doubly-fed motor. While adjusting the stator active power or reactive power, the grid-side current and the load-side current can be ensured to be within the allowable range.

[0115] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them.

Claims

1. A high-voltage brushless double-fed motor control method, characterized in that: include: Collect the load current of the doubly-fed generator; If the load current exceeds the load current limit, reducing the stator active power of the doubly-fed generator; The stator active power is reduced until the load current is less than the load current limit and the output of the double-fed motor is normal.

2. The high-voltage brushless doubly-fed motor control method according to claim 1, characterized in that: If the load current exceeds the load current limit, the stator power of the double-fed generator is reduced specifically as follows: According to a preset priority mode, reducing the stator power of the doubly-fed motor, the priority mode being divided into a grid-connected inversion priority and a load inversion priority; If the doubly-fed motor is in the grid-connected inversion priority, the stator power of the doubly-fed motor is reduced, specifically: a first variable is set to 1, and the size between the load current and the load current limit is determined, wherein the first variable is a constant and is greater than 0; If the load current is greater than the load current limit, reducing the stator active power by a first preset value; The magnitude between the load current and the load current limit is determined; if the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

3. The high-voltage brushless double-fed motor control method according to claim 2, characterized in that: The method further includes, if the doubly-fed motor is in a grid-connected inversion priority level, reducing the stator power of the doubly-fed motor, and further includes: If the load current is less than or equal to the load current limit, the first variable is set to the difference between the first variable and the first preset value, and the first variable is divided by the first preset value to obtain a third variable. If the third variable is greater than or equal to 1, the stator active power is increased by the first preset value.

4. The high-voltage brushless double-fed motor control method according to claim 2, characterized in that: The step of reducing the stator power under the grid-connected inverter priority also includes: If the load current is less than or equal to the load current limit, the load inversion priority is entered, and the stator power is reduced under the load inversion priority, which specifically includes: setting the second variable to 1; Determining the magnitude between the load current and the load current limit; The judgment result is that if the load current is greater than the load current limit, the size between the stator power and the rated power is judged, wherein the second variable is a constant and is greater than 0; If the stator power is greater than the rated power, the stator power is reduced by a second preset value.

5. The high-voltage brushless doubly-fed motor control method according to claim 4, characterized in that: Determining that the stator power is reduced under the load inversion priority also includes: If the load current is greater than the load current limit, the operation of reducing the stator active power is repeated.

6. The high-voltage brushless doubly-fed motor control method according to claim 4, characterized in that: Determining that the stator power is reduced under the load inversion priority also includes: If the load current is less than or equal to the load current limit, the second variable is set to the difference between the second variable and the second preset value, the second variable is divided by the second preset value, and if the second variable is greater than or equal to 1, the stator power is increased by a second preset value.

7. A high voltage brushless double-fed motor control device, characterized in that: The device comprises: An acquisition module is used to collect the load current of the double-fed generator; A processing module, configured to reduce the stator active power of the double-fed generator if the load current exceeds the load current limit; The stator active power is reduced until the load current is less than the load current limit and the output of the double-fed motor is normal.