TWI724557B - Estamating method for braking resistor - Google Patents

Abstract

An estimating method for a braking resistor, comprising steps of: (S1) confirming if performing in a generator mode; (S2) monitoring a bus voltage when in the generator mode; (S3) confirming if a switch is to be closed; (S4) calculating a first current value by a variation of the bus voltage during an open period, a vesting time of the open period and a known bus capacitor value when the switch is need to be closed; (S5) controlling the switch to be closed; (S6) confirming if the switch is to be opened; and (S7) calculating a second current value by a variation of the bus voltage during a closed period, a vesting time of the closed period and the known bus capacitor value when the switch is need to be opened, and then estimating a resistor value of the braking resistor.

Description

Estimation method of braking resistance

This case is about an estimation method, especially a method used in motor control systems to estimate the braking resistance of the motor control system.

The motor usually needs a motor control system for power supply and control. If the motor operates in generator mode, it converts mechanical energy into electrical energy and recharges it to the DC link voltage of the motor control system. If the power conversion circuit or rectifier circuit in the motor control system can only convert electric energy in one direction, the electric energy recharged by the motor to the motor control system cannot be incorporated into the mains. Therefore, the motor control system must be equipped with a braking resistor to take advantage of the braking. The resistor consumes the electric energy recharged by the motor in the form of heat, thereby avoiding the continuous increase of the DC link voltage and protecting the motor control system.

However, if the resistance value of the braking resistor used in the motor control system is not appropriate, excessive braking current will be generated. As a result, the life of the power switch existing in the discharge circuit of the motor control system will be reduced, and the power switch may even be burned. In severe cases, the motor control system cannot operate normally.

The purpose of this case is to provide a method for estimating the braking resistor. During the operation of the motor control system, the operating parameters of the motor control system are used to estimate the resistance value of the braking resistor, so as to confirm whether the braking resistor selected by the motor control system is Appropriate, so as to reduce the risk of burnout of the power switch due to the use of the wrong braking resistor.

To achieve the above objective, one implementation aspect of this case is to provide an estimation method applied to a motor control system. The motor control system controls the operation of the motor and drives the motor to brake when a generator mode is executed. The motor control system includes a busbar Capacitors, braking resistors and switches. The braking resistors are connected between the bus capacitors and switches. The estimation method includes the following steps: (S1) Confirm whether the motor control system starts to execute the generator mode; (S2) Confirm that the motor control system starts to execute In generator mode, continuously monitor the voltage of the bus capacitor; (S3) confirm whether the switch is switched to the ON state; (S4) when confirming that the switch is switched to the ON state, use both ends of the bus capacitor in the generator mode and the switch is switched to The voltage change during the off state until the switch is switched to the on state, the duration of the switch off and the known capacitance value of the bus capacitor, calculate the first current value flowing through the bus capacitor when the switch is off; (S5) The control switch is switched to the on state; (S6) to confirm whether the switch is switched to the off state; and (S7) to confirm that the switch is switched to the off state, use the bus capacitor in the generator mode and the switch is switched to the on state until the switch is switched For the voltage change during the off state, the duration of the switch on, and the known capacitance value of the bus capacitor, the second current value flowing through the bus capacitor when the switch is off is calculated to use the first current value and the second current value. The current value is used to estimate the resistance value of the braking resistor.

Some typical embodiments embodying the features and advantages of this case will be described in detail in the following description. It should be understood that the case can have various changes in different aspects, which do not depart from the scope of the case, and the descriptions and diagrams therein are essentially for illustrative purposes, rather than being constructed to limit the case.

Please refer to Figures 1A, 1B and Figure 2. Figures 1A and 1B are the step flow diagrams of the braking resistor estimation method of the preferred embodiment of this project, and Figure 2 is the estimation method shown in Figure 1 The schematic diagram of the circuit structure of the applied motor control system. As shown in Figures 1 and 2, the braking resistor estimation method in this case can be applied to a motor control system 1. The motor control system 1 can be, but is not limited to, an elevator motor control system, and is connected to the motor 2, for example The motor is electrically connected for supplying power to the motor 2 and controlling the operation of the motor 2. In this embodiment, the power conversion circuit or the rectifier circuit in the motor control system 1 may be unidirectional, that is, perform unidirectional electric energy conversion. In addition, the motor control system 1 can execute a motor (drive) mode or a generator (brake) mode (electric motor (drive) mode or generator (brake) mode). In the motor mode, the motor control system 1 will Input AC power for conversion to supply power to motor 2 and drive motor 2 to operate. On the contrary, in generator mode, motor control system 1 drives motor 2 to brake. At this time, motor 2 converts mechanical energy into electrical energy and recharges it. To the motor control system 1 or energy storage device (not shown).

Please refer to Figure 3 and cooperate with Figure 2. Figure 3 is the working quadrant diagram of the motor control system shown in Figure 2. In this embodiment, the motor control system 1 can be divided into four quadrants of operation. In detail, for example, when used in elevator motor control, the elevator has upstairs and downstairs operations. For the motor, it is rotating in one direction and rotating in the other direction, or so-called forward and reverse rotation; on the other hand, the elevator The output torque also has positive and negative values to meet the two requirements of the elevator's acceleration operation and deceleration operation, so it can be expanded into four operations based on the aforementioned motor forward or reverse and the output torque is positive or negative. Quadrant, for example, in this embodiment, the first quadrant is that the motor control system 1 drives the motor 2 to rotate forward. At this time, the speed of the motor 2>0, the torque of the motor 2>0, and the output power of the motor 2 P>0( In Figure 2, the different arrow directions represent the direction of electrical energy conversion of the motor control system 1 when the output power P is greater than 0 and less than 0, respectively. The second quadrant is that when motor 2 is in the forward rotation state, motor control system 1 drives motor 2 to brake. At this time, the speed of motor 2 is> 0, the torque of motor 2 is> 0, and the output power of motor 2 is P> 0. The third quadrant is that the motor control system 1 drives the motor 2 to reverse, the speed of the motor 2>0, the torque of the motor 2>0, and the output power of the motor 2 P>0. The fourth quadrant is that when the motor 2 is in the reverse state, the motor control system 1 drives the motor 2 to brake. At this time, the speed of the motor 2>0, the torque of the motor 2>0, and the output power of the motor 2 P>0. Therefore, when the motor control system 1 executes the motor mode, it can operate in the first quadrant or the third quadrant. When the motor control system 1 executes the generator mode, it can operate in the second quadrant or the fourth quadrant. The estimation method is performed when the motor control system 1 executes the generator mode, that is, when it is operating in the second quadrant or the fourth quadrant.

Please refer to FIG. 2, the motor control system 1 includes a power inverter module 10, a rectifying circuit 11, the bus capacitor C _BUS, the braking resistor R _B, S _B switch 12 and a voltage sensor. The rectifier circuit 11 is electrically connected to the input terminal of the motor control system 1 for rectifying the input AC power received by the input terminal of the motor control system 1 into DC power. The bus capacitor C _{Bus is} electrically connected to the output terminal of the rectifier circuit 11 to stabilize the DC power output by the rectifier circuit 11. Voltage sensor 12 is electrically connected to both ends of the bus capacitor C _Bus, for sensing bus voltage V _Bus bus capacitance measuring the C _Bus. Braking resistor R _B is electrically connected between the capacitor C _Bus busbar and a switch S _B, for charging energy to the motor control system 1, the motor 2 consumes backfilled control system of electric energy to the motor 1 back to the motor 2. Specifically, the braking resistor R _B S _B series with the switch, the brake resistor R _B, and S _B of the switch circuit further capacitance in parallel with the bus C _Bus. The input end of the inverter power module 10 is _{electrically connected to the bus capacitor C Bus} , the output end of the inverter power module 10 is electrically connected to the motor 2, and the inverter power module 10 is used to stabilize the voltage _{through the bus capacitor C Bus} The DC power is then converted into output AC power to drive the motor 2 to operate. S _B switch to the OFF state (opened status), the switch S _B may be in the motor control system 1 performs the generator mode when the motor control system 1 performs the motor off state or mode between a conducting state (closed status) To switch.

Please refer to Figures 4, 5, and 6 in conjunction with Figure 1. Figure 4 is the waveform diagram of some parameters of the motor control system when the motor control system shown in Figure 2 executes the generator mode. Figure 5 is the waveform diagram of some parameters of the motor control system. The motor control system shown in Figure 2 executes the generator mode and the switch is turned on. Figure 6 is the motor control system shown in Figure 2 executes the generator mode and the switch is off. Schematic. as the picture shows. First, the estimation method in this case is to first execute step S1 to confirm whether the motor control system 1 starts to execute the generator mode. When the check result in step S1 is YES, execution step S2, the voltage sensor 12 monitors continuously the bus voltage V _Bus The bus capacitor C _Bus. It should be noted that the method proposed in this case is to continuously monitor the bus voltage V _Bus to cooperate with step S3, step S6 or other steps described later.

--(1) ， 其中i _Cap為流過匯流排電容C _Bus的電流，C為匯流排電容C _Bus的電容值，且電容值通常為已知值，V _Bus為匯流排電容C _Bus的匯流排電壓，因此在確認開關S _B切換至導通狀態時，便可利用匯流排電容C _Bus於開關S _B為斷開期間的電壓變化，例如第4圖所示從時間t ₁時之電壓V ₁上升至時間t ₂時之電壓V ₂之間的差值，與開關S _B斷開的持續時間，例如時間t ₁至時間t ₂，及匯流排電容C _Bus的已知電容值而計算出在開關S _B斷開期間流過匯流排電容C _Bus之電流值，於此暫稱前述計算值為第一電流值，又因開關S _B在斷開情況下，電機2回充至電機控制系統1的回充電流i _Reg實際上等於流過匯流排電容C _Bus之電流(第一電流值)i _Cap，因此電機2回充至電機控制系統1的回充電流i _Reg為以下公式(2)所示:

--(2) ， 其中i _Reg亦等於電機2回充至電機控制系統1之功率P _Reg除以匯流排電容C _Bus的匯流排電壓V _Bus。 After step S2 is executed, step S3 is executed to confirm _{whether the switch SB} is switched to the on state. When it is confirmed from the result in step S3 is switched to the voltage changes until the period prior to conducting state, the switch S _B is turned off to perform step S4, using the recorded busbar capacitance C _Bus off state _{of the} switch S _B the duration and the known capacitance value of the capacitance C _Bus busbar, the busbar to determine the current of the capacitor C _Bus turned off during the switch S _B flows. More specifically, the duration of the switching means S _B OFF after the motor control system 1 starts executing the generator mode and the switch S _B is turned off, until the confirmation switch S _B is switched to the conducting state before the duration of the process. In step S3, the formula (1) of the current flowing through the bus capacitor C _{Bus is:}

--(1), where i _Cap is the current flowing through the bus capacitor C _Bus , C is the capacitance value of the bus capacitor C _Bus , and the capacitance value is usually a known value, and V _Bus is the bus current of the bus capacitor C _Bus discharge voltage, when the confirmation switch S _B is switched to the conducting state, the capacitor C _Bus bus can use _the switch S _B is a voltage variation during off, as shown in FIG. 4, voltage V ₁ is from time t ₁ when the up to a difference between the time t _2, and the duration of the switch S _B off voltage of ₂ V, for example, times t ₁ to time t _2, and the known capacitance value of the capacitance C _Bus bus is calculated in The value of the current flowing through the bus capacitor C _Bus during switch S _{B is} off. Here, the aforementioned calculated value is temporarily referred to as the first current value, and because switch S _B is off, the motor 2 is recharged to the motor control system 1 The regenerative current i _{Reg is} actually equal to the current (first current value) i _Cap flowing through the bus capacitor C _{Bus . Therefore, the regenerative} current i Reg that the motor 2 recharges to the motor control system 1 is given by the following formula (2) Show:

- (2), where i _Reg backfilled also equal to the motor 2 to the power of the motor control system 1 P _Reg bus voltage divided by the capacitance C _Bus V _Bus is bus.

--(3) 。 此外，在開關S _B為導通狀態下，流過制動電阻R _B之電流i _B(於此暫稱前述計算值為第三電流值)為電機2回充至電機控制系統1的回充電流i _Reg與流過匯流排電容C _Bus之電流i _Cap之相減值，即如以下公式(4)所示:

--(4)， 其中由於電機2回充至電機控制系統1的回充電流i _Reg在開關S _B由導通狀態切換至斷開狀態時的瞬間變化實際上並不大，故可將電機2回充至電機控制系統1的回充電流i _Reg在開關S _B為導通狀態時與斷開狀態時視為約略相等，因此公式(4)中的回充電流i _Reg可由公式(2)帶入，又因公式(4)中流過匯流排電容C _Bus之電流i _Cap，即第二電流值已由公式(3)求得，如此一來，便可估測出流過制動電阻R _B之電流i _B(第三電流值)。更甚者，由於在開關S _B導通狀態下，已知流過制動電阻R _B之電流i _B(第三電流值)，亦利用電壓感測器12而可得知匯流排電容C _Bus的匯流排電壓V _Bus，故可估測出制動電阻R _B之電阻值R _r，即如以下公式(5)所示:

--(5)。 When performed after step S4, step S5, the control switch S _B is switched to the conducting state, for example, t ₂ the control switch S _B is switched to the conducting state at a time. Then, step S6 is executed to confirm _{whether the switch SB} is switched to the off state. When the confirmation switch S _B is switched to the OFF state, then performing step S7, by using the bus capacitor C _Bus S _{B to} switch from a conducting state until the voltage is switched to the OFF state before the change of the period, switch S _B is turned on continuously time and the known capacitance value of the capacitance C _Bus bus, the switch S is calculated in the current flowing through the bus capacitor C _{Bus B} conduction period, this value is tentatively called the second current value is calculated. More specifically, the duration of the switch S _B is turned on refers to a motor control system 1 performs a switch S _B and a generator mode after conducting state until the confirmation switch S _B is switched to the OFF state before the duration. Then, use the subtraction value of the aforementioned first current value and the second current value to estimate _{the third current value flowing through the braking resistor R B} , and then use the bus capacitor C _Bus from the on state of the switch S _{B until it is switched to} voltage change during the period before the OFF state, divided by the third current value, to estimate the brake resistor R _B's. In step S6, when the confirmation switch S _B is switched to the OFF state, the voltage can change during _the bus capacitor C _Bus switch S _B is turned on, for example, as shown in Fig. 4 from the time t ₂ when the voltage V ₂ difference dropped to time t, and the duration of the switch conduction between S _{B 3 3} of the voltage V, for example, time t ₂ to time _{t. 3,} and the known capacitance value of the capacitance C _Bus bus bar calculated in the switch The current value flowing through the bus capacitor C _Bus when S _{B is} turned on is the second current value, where the second current value is shown in the following formula (3):

--(3). In addition, when the switch S _B is in the on state, the current i _{B flowing through the braking resistor R B} (herein tentatively referred to as the aforementioned calculated value is the third current value) is the recharging current i from the motor 2 to the motor control system 1 _The subtraction value of Reg and the current i _Cap flowing through the bus capacitor C _Bus is as shown in the following formula (4):

- (4), where since the motor 2 backfilled back to the motor control system 1 is instantaneously changes the charge current i _Reg switched from ON state to the OFF state the switch S _B is not actually large, so that the motor may be 2 backfilled back to the motor control system of the charging current i _Reg 1 when the switch S _B is considered roughly equal to a conducting state and disconnected state, back to the formula (4) in the charge current i _Reg by the formula (2) into the , And because the current i _Cap flowing through the bus capacitor C _{Bus in} formula (4), that is, the second current value has been calculated by formula (3), in this way, the current flowing through the braking resistor R _{B can be estimated} i _B (third current value). What is more, since the switch S _B in the conducting state, the current i _B flowing through a known resistor R _B of the brake (the third current value), but also by the voltage sensor 12 that the bus may be the bus capacitor C _Bus The row voltage is V _Bus , so the resistance value R _r of the braking resistor R _B can be estimated, as shown in the following formula (5):

--(5).

In the above embodiment, when the confirmation result of step S1 is no, step S1 is executed again. When the confirmation result of step S3 is no, step S3 is executed again. When the confirmation result of step S6 is no, step S6 is executed again. Further, when performed after the step S7, the switch S _B is switched to the OFF state, and if necessary, the case can be re-estimation method step S1 a new estimate.

In some embodiments, in step S3, the capacitance C _Bus is a bus based on the voltage bus V _Bus has risen to the first predetermined voltage threshold value to confirm whether the switch S _B is switched to the conducting state. In step S6, it is determined _{whether the switch S B} is switched to the off state according to whether the bus voltage V _{Bus of the bus capacitor C Bus} drops to the second preset voltage threshold value, but it is not limited to this. In step S6 , also based on duration of the switch S _B is turned on reaches the predetermined time threshold to confirm whether the switch S _B is switched to the OFF state.

In summary, this case provides an estimation method for braking resistor estimation. This estimation method can use the operating parameters of the motor control system to estimate the resistance value of the braking resistor when the motor control system executes the generator mode. Therefore, the user can use the estimated resistance value of the braking resistor to evaluate whether the resistance value of the braking resistor currently used in the motor control system is appropriate, so that when it is not applicable, the user can re-select the appropriate braking resistor or turn on the relevant The protection mechanism, in this way, will extend the life of the power switch existing in the discharge circuit of the motor control system, and prevent the power switch of the motor control system from burning.

S1~S7: Step 1 of the estimation method: Motor control system 2: Motor P: Output power 10: Inverter power module 11: Rectifier circuit 12: Voltage sensor C _Bus : Bus capacitor R _B : Braking resistor S _B : Switches V ₁ , V ₂ , V ₃ : Voltage t ₁ , t ₂ , t ₃ : Time V _Bus : Bus voltage i _cap : Current i _{Reg of} bus capacitor C _Bus : Recharging current i _B : Braking resistance R _B 's current i _B

Figures 1A and 1B are schematic diagrams of the steps of the braking resistor estimation method of the preferred embodiment of the present invention; Figure 2 is a schematic diagram of the circuit architecture of the motor control system to which the estimation method shown in Figure 1 is applied; Figure 3 is the working quadrant diagram of the motor control system shown in Figure 2; Figure 4 is a schematic diagram of waveforms of some parameters of the motor control system when the motor control system shown in Figure 2 executes the generator mode; Figure 5 is a partial structural diagram of the motor control system shown in Figure 2 executing generator mode and the switch is turned on, and Figure 6 is the motor control system shown in Figure 2 executing generator mode; Figure 6 is a schematic diagram of part of the structure when the motor control system shown in Figure 2 executes the generator mode and the switch is off.

S1~S7: Steps of the estimation method

Claims (9)

An estimation method applied to a motor control system that controls the operation of a motor and drives the motor to brake when a generator mode is executed. The motor control system includes a bus capacitor, a braking resistor, and a switch The braking resistor is connected between the busbar capacitor and the switch. The estimation method includes the following steps: (S1) confirm whether the motor control system starts to execute the generator mode; (S2) confirm the start of the motor control system When executing the generator mode, continuously monitor the voltage across the bus capacitor; (S3) confirm whether the switch is switched to a conducting state; (S4) use the bus capacitor when confirming that the switch is switched to the conducting state Both ends are in the generator mode and the switch is switched to an off state until the switch is switched to the on state, the duration of the switch off and a known capacitance value of the bus capacitor are calculated When the switch is off, a first current value flows through the bus capacitor; (S5) controls the switch to switch to the on state; (S6) confirms whether the switch is switched to the off state; and (S7) confirms When the switch is switched to the off state, the two ends of the bus capacitor are used in the generator mode and the switch is switched to the on state until the switch is switched to the off state. The voltage change and the duration of the switch on And the known capacitance value of the bus capacitor, calculate a second current value flowing through the bus capacitor when the switch is turned on, so as to estimate the value of the subtraction of the first current value and the second current value A third current value that flows through the braking resistor, and the voltage change of the bus capacitor from the on-state of the switch to the off-state is divided by the third current value to estimate the braking The resistance value of one of the resistors. The estimation method according to claim 1, wherein the estimation method is executed when the motor is in a forward rotation state and the motor control system drives the motor to brake. The estimation method according to claim 1, wherein the estimation method is executed when the motor is in a reverse state and the motor control system drives the motor to brake. The estimation method according to claim 1, wherein in the step (S3), it is determined whether the switch is switched to the on state according to whether the voltage across the bus capacitor rises to a first preset voltage threshold . The estimation method according to claim 1, wherein in the step (S6), it is determined whether the switch is switched to the off according to whether the voltage across the bus capacitor drops to a second preset voltage threshold status. The estimation method according to claim 1, wherein in the step (S6), it is determined whether the switch is switched to the off state according to whether the duration of the switch in the on state reaches a preset time threshold . The estimation method according to claim 1, wherein in the step (S1), the motor control system further includes an inverter power module and a rectifier circuit, and the inverter power module is electrically connected to the bus capacitor The motor is electrically connected to an output terminal of the inverter power module, and the bus capacitor is electrically connected to an output terminal of the rectifier circuit to execute the generator mode. The estimation method according to claim 7, wherein in the step (S1), when the motor control system executes the generator mode, the rectifier circuit performs a one-way electric energy conversion so that the switch can be opened at the Switch between the state and the on state. The estimation method according to claim 1, wherein in the step (S2), (S4) or (S7), the motor control system further includes a voltage sensor for sensing both ends of the bus capacitor The voltage.

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