阅读说明：本技术 一种精确补偿逆变器非线性损失的方法及系统 (method and system for accurately compensating nonlinear loss of inverter ) 是由 樊胜利 于 2019-10-12 设计创作，主要内容包括：本发明公开了一种精确补偿逆变器非线性损失的方法,包含以下步骤：步骤S1,在电机未运转时,向电机中注入多组不同数值的电流和载波频率信号,计算每个桥臂在不同电流和载波频率信号所对应的补偿参数T<Sub>dly</Sub>和V<Sub>on</Sub>；步骤S2,将不同数值的电流和载波频率信号和所对应的补偿参数T<Sub>dly</Sub>和V<Sub>on</Sub>制成电子数据并录入逆变器的储存器中；步骤S3,在电机正常运转时,利用所述步骤S2中的电子数据和线性插值方法计算每个桥臂所对应的补偿参数T<Sub>dly</Sub>和V<Sub>on</Sub>,计算每个桥臂所对应的非线性损失并分别进行补偿。本发明的有益效果是：1.本发明不增加及改动现有逆变器的硬件,成本低。2.本发明考虑了不同桥臂、不同开关频率、不同电流时的特性差异,可对非线性损失进行精准的补偿。(The invention discloses a method for accurately compensating nonlinear loss of an inverter, which comprises the following steps of S1, injecting a plurality of groups of current and carrier frequency signals with different values into a motor when the motor does not run, and calculating a compensation parameter T corresponding to different current and carrier frequency signals of each bridge arm dly And V on (ii) a Step S2, the current and carrier frequency signals with different values and the corresponding compensation parameter T dly And V on Making electronic data and recording the electronic data into a storage of the inverter; step S3, when the motor is running normally, the electronic data and the linear interpolation method in the step S2 are used for calculating the compensation parameter T corresponding to each bridge arm dly And V on And calculating the nonlinear loss corresponding to each bridge arm and respectively compensating. The invention has the beneficial effects that: 1. the invention does not increase and change the hardware of the existing inverter and has low cost. 2. The invention considers different bridge arms,The nonlinear loss can be accurately compensated by the characteristic difference of different switching frequencies and different currents.)

1, methods for accurately compensating nonlinear loss of an inverter, comprising the steps of:

step S1, when the motor is not running, injecting a plurality of groups of current and carrier frequency signals with different values into the motor, and calculating the compensation parameter T corresponding to each bridge arm in different current and carrier frequency signals_dlyAnd V_on；

Step S2, the current and carrier frequency signals with different values and the corresponding compensation parameter T_dlyAnd V_onMaking electronic data and recording the electronic data into a storage of the inverter;

step S3, when the motor is running normally, the electronic data and the linear interpolation method in the step S2 are used for calculating the compensation parameter T corresponding to each bridge arm_dlyAnd V_onAnd calculating the nonlinear loss corresponding to each bridge arm and respectively compensating.

2. The method for accurately compensating nonlinear loss of an inverter according to claim 1, wherein the step S1 is specifically performed in

S11, when the motor does not operate, closing the C-phase bridge arm switching tube, injecting current between the A-phase bridge arm and the B-phase bridge arm in a current closed-loop mode, and obtaining the equivalent parameter T when the C-phase bridge arm does not operate_dly1' and V_on1’；

S12, when the motor does not operate, the switching tube of the B-phase bridge arm is closed, current is injected between the A-phase bridge arm and the C-phase bridge arm in a current closed loop mode, and the equivalent parameter T when the B-phase bridge arm does not operate is obtained_dly2' and V_on2’；

S13, when the motor does not operate, closing the switch tube of the A-phase bridge arm, injecting current between the B-phase bridge arm and the C-phase bridge arm in a current closed-loop mode, and obtaining the equivalent parameter T when the A-phase bridge arm does not operate_dly3' and V_on3’；

S14, according to T_dly1' and V_on1’、T_dly2' and V_on2’、T_dly3' and V_on3' calculating compensation parameter T corresponding to each bridge arm at different current and carrier frequency signals_dlyAnd V_on。

3. The method for precisely compensating nonlinear loss in inverter of claim 2, wherein in steps S11, S12 and S13, N is injected while keeping current amplitude constant₂Grouping currents of different carrier frequency signals and then respectively maintaining N₂Personal loadThe frequency of the wave signal is not changed, and N is injected₁Grouping currents of different current amplitudes to obtain corresponding N₁*(N₂-1) equivalent parameters for each leg of the set when not in operation; n is a radical of₁Is a natural number of not less than 3, N₂Is a natural number not less than 2.

4. The method for precisely compensating nonlinear loss in inverter of claim 1, wherein in step S2, the electronic data is a two-dimensional table with current amplitude and carrier frequency as coordinates.

5. The method for accurately compensating nonlinear loss of an inverter according to claim 1, wherein in step S3, when the motor is running, the compensation parameters of different bridge arms are respectively calculated according to the determined current amplitude and carrier frequency, the nonlinear compensation time of different bridge arms is determined, and the compensation is respectively performed on different bridge arms.

A system for accurately compensating for nonlinear losses in an inverter, said system being capable of implementing the method of claim 1.

Technical Field

The invention relates to the technical field of power control, in particular to methods and systems for accurately compensating nonlinear loss of an inverter.

Background

The variable frequency driving system of the alternating current motor is constructed by a three-phase inverter shown in fig. 1 in the current engineering , because the upper and lower tubes of the bridge arm are in complementary conduction, dead time sections must be inserted into a driving signal to prevent the occurrence of a 'through' phenomenon, the artificially inserted dead time sections cause the loss of the output voltage of the inverter, and besides factors, the turn-on time and the turn-off time of switching tubes (VT 1-VT 6) and the conduction voltage drops of the switching tubes and freewheeling diodes (VD 1-VD 6) all cause the loss of the output voltage.

The method comprises the steps that voltage output by an inverter to a motor in an extremely low speed region is even lower than nonlinear loss voltage, so that the nonlinear loss needs to be accurately compensated if high-performance operation of the motor in the extremely low speed region is realized, the nonlinear loss compensation has two key points, wherein is direction judgment of phase current (iA, iB and iC), and the other is proper compensation voltage is set.

According to the prior art, taking phase a as an example, the equivalent time of the nonlinear loss is:

wherein, T_dSSetting of upper and lower tube dead time for software, T_onAnd T_offFor actual turn-on and turn-off delays, V_satIs the conduction voltage drop of the switching tube, V_dIs the conduction voltage drop of a freewheeling diode, D₁Or D₂For the upper tube opening ratio, F_pwmFrequency, V, of PWM carrier_dcIs the dc bus voltage.

In equation (1), when the positive and negative magnitudes of the phase current are the same, D₁+D₂As 1.0, it can be known that the forward and reverse nonlinear loss equivalent times are the same, so equation (1) can be replaced by equation (2) in engineering:

wherein, T_dly＝T_on-T_off，

V_on＝DV_sat-(1-D)V_d

In the above formula D is used instead of D₁Or (1-D)₂) The identification of the nonlinear equivalent time by the prior method is limited to T_dEPerforming identification, wherein the turn-on and turn-off delay T cannot be identified respectively_dlyAnd the conduction voltage drop V of the switch tube or the freewheel diode_onAnd the nonlinear equivalent parameters of each bridge arm cannot be identified, so that the compensation effect is poor when the switching frequency changes, and accurate compensation of each phase of bridge arm cannot be realized.

Disclosure of Invention

In order to overcome all or part of the defects in the prior art, the invention provides methods and systems for accurately compensating the nonlinear loss of the inverter, which are realized by the following technical scheme.

method for precisely compensating nonlinear loss of inverter includes the steps of S1, when the motor is not running, injecting a plurality of groups of current and carrier frequency signals with different values into the motor, and calculating compensation parameter T corresponding to different current and carrier frequency signals of each bridge arm_dlyAnd V_on(ii) a Step S2, the current and carrier frequency signals with different values and the corresponding compensation parameter T_dlyAnd V_onMaking electronic data and recording the electronic data into a storage of the inverter; step S3, when the motor is running normally, the electronic data and the linear interpolation method in the step S2 are used for calculating the compensation parameter T corresponding to each bridge arm_dlyAnd V_onAnd calculating the nonlinear loss corresponding to each bridge arm and respectively compensating.

, the concrete step of the step S1 is S11, when the motor is not running, the switch tube of the C-phase bridge arm is closed, and current is injected between the A-phase bridge arm and the B-phase bridge arm in a current closed loop mode to obtain the equal time when the C-phase bridge arm does not workEfficiency parameter T_dly1' and V_on1'; s12, when the motor does not operate, the switching tube of the B-phase bridge arm is closed, current is injected between the A-phase bridge arm and the C-phase bridge arm in a current closed loop mode, and the equivalent parameter T when the B-phase bridge arm does not operate is obtained_dly2' and V_on2'; s13, when the motor does not operate, closing the switch tube of the A-phase bridge arm, injecting current between the B-phase bridge arm and the C-phase bridge arm in a current closed-loop mode, and obtaining the equivalent parameter T when the A-phase bridge arm does not operate_dly3' and V_on3'; s14, according to T_dly1' and V_on1’、T_dly2' and V_on2’、T_dly3' and V_on3' calculating compensation parameter T corresponding to each bridge arm at different current and carrier frequency signals_dlyAnd V_on。

, in steps S11, S12 and S13, N is injected while keeping the current amplitude constant₂Grouping currents of different carrier frequency signals and then respectively maintaining N₂The frequency of each carrier signal is not changed, and N is injected₁Grouping currents of different current amplitudes to obtain corresponding N₁*(N₂-1) equivalent parameters for each leg of the set when not in operation; n is a radical of₁Is a natural number of not less than 3, N₂Is a natural number not less than 2.

, in step S2, the electronic data is a two-dimensional table with current magnitude and carrier frequency as coordinates.

, in step S3, when the motor is running, the compensation parameters of different bridge arms are respectively calculated according to the determined current amplitude and carrier frequency, the nonlinear compensation time of different bridge arms is determined, and the compensation is respectively performed on the different bridge arms.

Further , the system can implement the method of claim 1.

The invention has the beneficial effects that:

1. the invention does not increase and change the hardware of the existing inverter and has low cost.

2. The invention considers the characteristic difference of different bridge arms, different switching frequencies and different currents, and can accurately compensate the nonlinear loss.

Drawings

Fig. 1 is a circuit diagram of a variable frequency driving system of a three-phase inverter and an ac motor in the prior art.

FIG. 2 is a schematic flow diagram of the process of the present invention.

Fig. 3 is a schematic diagram of the motor versus nonlinear loss flow of the present invention.

Fig. 4 is a schematic diagram of the working principle of the system of the invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only partial embodiments of of the present invention, rather than all embodiments.

The following describes the steps of the present invention:

1. calculating equivalent parameter T when C-phase bridge arm does not work_dly1' and V_on1'. And closing the C-phase bridge arm switching tube, and injecting current between the A-phase and the B-phase in a current closed-loop mode, wherein: i.e. i_A＝-i_BPhase of current i of phase A_APositive direction, C phase current i_CIs zero.

Step 1.1, first, a current with amplitude I1 is injected, and carrier frequency F_pwmEqual to F1, sampling the command voltage V after the current reaches the steady state _ref1. Bus voltage V _dc1 and phase current I_s1; the equivalent nonlinear loss time, recorded as T, is found from equation (3)_dE1。

R in the above formula (3)_SBeing stator resistors of electric machines

Step 1.2, maintaining the current amplitude I1 unchanged, switching the carrier frequency to F2, and sampling the instruction voltage V after the current reaches a steady state_ref2. Bus voltage V_dc2 and phase current I_s2; the equivalent nonlinear loss time, recorded as T, is found from equation (3)_dE2。

From these two sets of data, the following set of equations is established in conjunction with equation (2):

solving the equation set (4) to obtain sets of T_dly1' and V_on1', denoted by Par1(1, 1).

Step 1.3, maintaining the current amplitude I1 unchanged, switching the carrier frequency to F3, collecting data after the current reaches a steady state, and obtaining another groups of T according to simultaneous equations of sampling data of F2 and F3 and solving (refer to steps 1.1-1.2)_dly1' and V_on1', denoted by Par1(1, 2).

Step 1.4, keeping the current amplitude I1 unchanged, and switching the carrier frequency until FN₂To obtain corresponding Par1(1,3), … …, Par1(1, N)₂-1)。Par1(1,N₂-1) when the C-phase bridge arm is not in operation, the current amplitude is I1, and the carrier frequency is F (N)₂-1) Change to FN₂Corresponding equivalent parameter T_dly1' and V_on1’。

Step 1.5, change the current amplitude to I2, adjust the carrier frequency to F1, F2, F3, … …, F (N)₂-1)、FN₂And calculating to obtain Par1(2,1), Par1(2,2), … … and Par1(2, N)₂-1)。

Par1(2,N₂-1) when the C-phase bridge arm is not in operation, the current amplitude is I2, and the carrier frequency is F (N)₂-1) Change to FN₂Corresponding equivalent parameter T_dly1' and V_on1’。

Step 1.6, change the current amplitude to I3, adjust the carrier frequency to F1, F2, F3, … …, F (N)₂-1)、FN₂And calculating to obtain Par1(3,1), Par1(3,2), … … and Par1(3, N)₂-1)。

Par1(3,N₂-1) when the C-phase bridge arm is not in operation, the current amplitude is I3, and the carrier frequency is F (N)₂-1) Change to FN₂Corresponding equivalent parameter T_dly1' and V_on1’。

Step 1.7, change the current amplitude to IN₁The carrier frequencies are adjusted to F1, F2, F3, … …, F (N)₂-1)、FN₂And calculating to obtain Par1 (N)₁,1)，Par1(N₁,2),……,Par1(N₁,N₂-1)。

Par1(N₁,N₂-1) current amplitude IN when C-phase bridge arm is not working₁Carrier frequency from F (N)₂-1) Change to FN₂Corresponding equivalent parameter T_dly1' and V_on1'. And after data acquisition and calculation are finished, the current is reduced to zero, and output is blocked.

2. Calculating equivalent parameter T when B-phase bridge arm does not work_dly2' and V_on2’。

Closing the switch tube of the B-phase bridge arm, injecting current i between the A-phase bridge arm and the C-phase bridge arm in a current closed loop mode_C＝-i_APhase i of C current_CIs positive, phase B current i_BIs zero. According to the procedure of step 1, Par2(i,1), Par2(i,2), … …, Par2(i, N) were obtained₂-1), where i denotes the index number of the current amplitude, i ═ 1,2, 3, … …, N₁。

3. Calculating identification equivalent parameter T when A-phase bridge arm does not work_dly3' and V_on3’。

Closing the switch tube of the A-phase bridge arm, injecting current i between the B-phase bridge arm and the C-phase bridge arm in a current closed loop mode_B＝-i_CPhase B current i_BPositive direction, phase A current i_AIs 0. According to the procedure of step 1, Par3(i,1), Par3(i,2), … …, Par3(i, N) were obtained₂-1), where i denotes the index number of the current amplitude, i ═ 1,2, 3, … …, N₁。

The T obtained in the steps 1,2 and 3_dly1' and V_on1’、T_dly2' and V_on2’、T_dly3' and V_on3' described using table 1.

TABLE 1

4. Calculate T per phase leg_dlyAnd V_on。

Because the driving circuits of the switching tubes of each -phase bridge arm are independent, the characteristics of the switching tubes and the freewheeling diodes can be different, and the phase resistance of the motor is not completely , the compensation parameters of each phase are required to be obtained for separate compensation in order to achieve a relatively ideal compensation effect.

According to the working modes of the switching tube in the steps 1-3, the equivalent parameter obtained in the step 1 is actually the average value of the A-phase compensation parameter and the B-phase compensation parameter, the equivalent parameter obtained in the step 2 is actually the average value of the A-phase compensation parameter and the C-phase compensation parameter, and the equivalent parameter obtained in the step 3 is actually the average value of the B-phase compensation parameter and the C-phase compensation parameter.

The compensation parameters of the three bridge arms are respectively as follows:

ParA(i,n)＝[Par1(i,n)+Par2(i,n)+Par3(i,n)]–2*Par3(i,n)

ParB(i,n)＝[Par1(i,n)+Par2(i,n)+Par3(i,n)]–2*Par2(i,n)

ParC(i,n)＝[Par1(i,n)+Par2(i,n)+Par3(i,n)]–2*Par1(i,n)

in the above formula, i is 1,2, 3, … …, N₁,n＝1、2、……、N₂-1. To ensure compensation accuracy, N₁Value of not less than 3, N₂The value is not less than 2, and the calculation result is shown in table 2:

TABLE 2

5. Table 2 is made into electronic data and recorded into a power-down conservation memory of the control portion of the three-phase inverter the process of steps 1-4 typically only needs to be performed times, unless the motor is replaced or the inverter configuration is changed.

6. The motor compensates for non-linear losses while operating. While the motor is runningFor phase a, for example, the column number in table 2 is first determined according to the current carrier frequency, and is denoted as N (N is 1,2, 3, … …, N)₂-1), then according to the A-phase current magnitude i_AI select lines Ii and Ii +1 (i ═ 1,2, 3, … …, N₁-1), using the values of n columns as interpolation reference, and calculating the compensation parameter of the A phase according to the following formula; in the formula, when the carrier frequency is larger than FN₂When N is equal to N₂-1, when the carrier frequency is less than F₁When n is 1, the number n is equal to 1.

Wherein, ParaA ═ T_dlyA,V_onA}

Obtaining the nonlinear equivalent parameter T of the A-phase bridge arm_dlyA and V_onAfter A, setting the current dead time T_dSCurrent carrier frequency F_pwmThe current DC bus voltage V_dc and substituting into equation 2 to obtain the nonlinear compensation time T of phase A_dEA。

The nonlinear compensation time T of the B-phase bridge arm and the C-phase bridge arm can be obtained by the same method_dEB and T_dEC. The process described in step 6 can be described by the flow chart shown in fig. 3.

To obtain T_dEA、T_dEB and T_dEAnd C, performing nonlinear loss time compensation on each bridge arm according to the direction of the phase current: when the phase current direction is positive, the nonlinear compensation time is positive, and when the phase current direction is negative, the nonlinear compensation time is negative.

In the present invention, it is easy to think that the steps 1,2 and 3 are in parallel relation and do not have a specific sequence relation.

In a specific embodiment, the system is under the following conditions (N)₁＝3,N₂＝3；I₁＝0.15I_N,I₂＝0.5I_N,I₃＝0.8I_N；F₁＝1kHz,F₂＝4kHz,F₃＝8kHz，I_NAs rated current of the inverter) are shown in table 3:

TABLE 3

A system for precisely compensating nonlinear loss of inverter is prepared as enabling to identify nonlinear parameter times when motor is not running, calculating out voltage command by unit 5 according to current command of step 1-3 and sending it to unit 2, calculating out three-phase duty ratio time by unit 2 and sending it to unit 4, outputting driving signal to unit 7 by unit 4, outputting voltage pulse to motor by unit 7, sending detected phase current and bus voltage to unit 5 by unit 7, controlling phase current and carrier frequency by unit 5 according to detected value and calculating nonlinear equivalent parameter according to requirement of step 1-3, storing identification result to unit 6 after identification is finished.

2. When the motor runs, the unit 1 generates a voltage instruction and sends the voltage instruction to the unit 2, the unit 2 calculates the three-phase duty ratio time and sends the three-phase duty ratio time to the unit 3, the unit 3 calculates the current nonlinear compensation value in real time according to the nonlinear identification parameter in the memory, the detected phase current and the bus voltage, the calculation result of the unit 2 is compensated and then sent to the unit 4, the unit 4 outputs a driving signal to the unit 7, and the voltage output by the unit 7 is the output voltage after accurate compensation.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.