WO2016050045A1

WO2016050045A1 - Variable-frequency air conditioner control method

Info

Publication number: WO2016050045A1
Application number: PCT/CN2015/076184
Authority: WO
Inventors: 王斌
Original assignee: 海信科龙电器股份有限公司; 广东科龙空调器有限公司
Priority date: 2014-09-30
Filing date: 2015-04-09
Publication date: 2016-04-07
Also published as: CN104534631A; CN104534631B

Abstract

A variable-frequency air conditioner control method, applicable in a variable-frequency air conditioner controller, comprising: performing a compensation control on a q-shaft current in a compressor, where the compensation method is such that: updating a q-shaft current command value on the basis of a main circuit bus voltage, Vp, and participating in a conventional FOC vector algorithm, increasing the q-shaft current command value when Vp rises, and decreasing the q-shaft current command value when Vp drops.

Description

Inverter air conditioner control method

Technical field

The present invention relates to the field of inverter air conditioners, and more particularly to an inverter air conditioner control method.

Background technique

The inverter air conditioner is a special compressor for frequency conversion based on the ordinary air conditioner, and the frequency conversion control system is added. The main unit of the inverter air conditioner is automatically steplessly variable, which can automatically provide the required amount of cold (heat) according to the indoor situation; when the indoor temperature reaches the desired value, the air conditioner main unit operates at a constant speed that can accurately maintain this temperature. Achieve "no downtime" to ensure stable ambient temperature.

In the prior art, the variable frequency control system is generally referred to as a variable frequency controller. The frequency conversion controller is usually a frequency converter of "AC-DC-AC" circuit structure. Its working principle is that AC power is obtained by the rectifier circuit to obtain DC power, and then filtered by the electrolytic capacitor. Finally, the AC voltage of the inverter circuit is adjustable. Drive the inverter compressor to work. On the one hand, such an inverter controller has a large electrolytic capacitor and a high cost, and at the same time, the controller is bulky due to the large electrolytic capacitor capacity.

Summary of the invention

The present invention provides a low-cost inverter air conditioner control method for overcoming at least one of the above-mentioned drawbacks (deficiencies) of the prior art.

In order to solve the above technical problem, the technical solution of the present invention is as follows:

An inverter air conditioner control method, the method is applied to an inverter air conditioner controller, wherein the controller comprises a main control MCU, a rectification and PFC unit circuit, a three-phase inverter circuit, an AC voltage detecting unit connected to the main control MCU, and The main circuit bus voltage detection circuit, the main control MCU is connected with the compressor phase current iU/iV detection signal, the main control MCU drives the three-phase inverter circuit through the inverter drive circuit and drives the PFC unit through the PFC drive circuit, in the rectification and A storage capacitor C is connected between the PFC unit circuit and the three-phase inverter circuit; the method includes:

The q-axis current in the compressor is compensated and controlled. The compensation mode is: update the q-axis current command value according to the main circuit bus voltage Vp and participate in the traditional FOC vector algorithm, and increase the q-axis current command value when Vp rises, and adjust the V-axis current command value when Vp rises. Low q-axis current command value.

In the present invention, the main circuit bus voltage detecting circuit detects the main circuit bus voltage Vp, and then according to Vp updates the command value of the q-axis current to complete the compensation of the q-axis current. When Vp rises, the q-axis current command value is increased. When Vp falls, the q-axis current command value is lowered to make the Vp and q-axis current command values. Matching, the output of higher electric power is achieved at a higher voltage in a half-frequency cycle, and the lower electric power is output at a lower voltage, thereby significantly reducing the demand for the storage capacitor capacity and increasing the power density of the controller. Reduce the size of the controller and reduce costs.

In a further solution, the compensation mode is specifically: generating a modulation coefficient Mv according to the main circuit bus voltage Vp, and multiplying the Mv by the q-axis current command value as a new q-axis current command value to participate in the conventional FOC vector algorithm.

The specific way to generate a modulation factor Mv according to the main circuit bus voltage Vp is:

Construct a function f(Vp/V_p) with Vp/V_p as an independent variable, let: the modulation coefficient Mv=f(Vp/V_p), V_p the average value of the main circuit bus voltage Vp in a long period T time; The function f(Vp/V_p) can take many forms.

The two types with more practical value are listed as follows:

When weak compensation control is performed, the modulation coefficient Mv=(Vp/V_p) ^1/N , where N=2 or 3, V_p is the average value of the main circuit bus voltage Vp in a long period T time;

When stronger compensation control is required, the modulation coefficient Mv=(Vp/V_p) ^N , where N=1 or 2, V_p is the average value of the main circuit bus voltage Vp over a long period T time.

The invention obtains the instantaneous voltage value Vp of the bus voltage by detecting the DC voltage Vp value of the main circuit bus, and averages Vp in a period T to obtain an average value V_p, where T is a continuous T time before the current adoption period. In the segment, the ratio of Vp/V_p is used to obtain the fluctuation ratio of the DC voltage of the bus. This voltage fluctuation ratio is used as the compensation parameter to compensate the iq current. In the d_q rotating coordinate system, the q-axis current is used for work. The compensation can output a large power when the voltage fluctuation ratio is high, and the output power becomes small when the fluctuation is small.

In a further aspect, the method further includes performing a field weakening control on the compressor, specifically:

The idref is set according to the main circuit bus voltage Vp, and the idref value is adjusted when i _q and i _d satisfy the following formula, otherwise the idref value is controlled according to the non-compensation method:

(L _q ×i _q ) ² +(L _d ×i _d +ψ) ² =(Vp-k) ² /(3×ω ² )

Where k is a constant greater than zero and less than Vp;

And when the idref value is adjusted, i _q , i _d must meet the following conditions:

(L _q ×i _q ) ² +(L _d ×i _d +ψ) ² ≤(Vp-k) ² /(3×ω ² )

Where Ld is the d-axis inductance, Lq is the q-axis inductance, ω is the compressor speed, ψ is the compressor rotor flux, i _d is the d-axis current of the compressor, i _q is the q-axis current of the compressor, and idref is The d-axis current command value of the compressor. The value of k is used to avoid the detection error of the Vp value, so that the controller should enter the field weakening control without entering the field weakening control, and the k value is a reserved deviation voltage value.

The invention can avoid voltage saturation at the bottom of the bus DC voltage by the field weakening control.

In a further scheme, the main circuit bus current io is also involved in the compensation control of the q-axis current, specifically to obtain the main circuit bus current io, and further transform the modulation coefficient Mv into Mv', wherein the modulation coefficient Mv'=(Mv-1)× (iorms/I)+1, where I is a constant and iorms is the effective value of the main circuit bus current io. When the controller performs the compensation control, the output power is small when the controller is running at a low frequency. At this time, the energy storage effect of the electrolytic capacitor is relatively good, so the compensation amount can be appropriately reduced at this time to improve the compressor noise during low frequency operation. The problem is that by changing the Mv value, the amount of compensation can be reduced, and the compressor noise problem at low frequency operation can be improved.

In a further solution, the capacitance of the storage capacitor C is less than the product of the maximum allowable output power of the inverter air conditioner controller of 0.5 μF/W. By using the q-axis current for compensation control and using a small storage capacitor, on the one hand, the effective volume of the controller can be significantly reduced, the cost of the controller can be reduced, the power density of the controller can be increased, and more importantly, the compensation can be controlled. Cooperating, the bus ripple voltage on the storage capacitor does not rise significantly when the capacity of the storage capacitor is reduced, and the rise of the bus ripple voltage is reduced.

In a further solution, the rectifying and inductive branch in the PFC unit circuit of the PFC unit circuit has a damping resistor in series. Since the inductor exists in the PFC circuit, and the compressor is a load with inductive characteristics, an unstable oscillating circuit structure is formed when combined with the storage capacitor. By setting the damper circuit, the oscillating amplitude can be effectively reduced, and the stability of the controller is provided. .

In a further solution, the resistance of the damping resistor is greater than or equal to 0.1 ohms.

Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

In the present invention, the main circuit bus voltage detecting circuit detects the main circuit bus voltage Vp, and then updates the command value of the q-axis current according to Vp, thereby completing the compensation of the q-axis current, and increasing the q-axis current command value when Vp rises. When Vp falls, the q-axis current command value is lowered to match Vp with the q-axis current command value, so that a higher electric power is output at a higher voltage in a half-duty cycle, and a lower output at a lower voltage. Electric power, which significantly reduces the need for storage capacitor capacity, increases the power density of the controller, reduces the size of the controller, and thus reduces costs.

DRAWINGS

Figure 1 is a block diagram of the circuit of the present invention.

2 is a block diagram of the algorithm control principle of the present invention.

Figure 3 is a block diagram of the circuit with interleaved PFC.

1. Rectifier and PFC unit circuit; 2. AC voltage monitoring unit; 3. Main circuit bus current detection circuit; 4. Main circuit bus voltage detection circuit; 5. Inverter drive circuit; 6. Three-phase inverter circuit; PFC drive circuit; 8, master MCU.

detailed description

The drawings are for illustrative purposes only and are not to be construed as limiting the invention;

In order to better illustrate the embodiment, some components of the drawings may be omitted, enlarged or reduced, and do not represent the actual product size;

It will be apparent to those skilled in the art that certain known structures and their description may be omitted.

In the description of the present invention, it is to be understood that the orientation or positional relationship of the terms "", "", and the like is based on the orientation or positional relationship shown in the drawings, and is merely for convenience of description of the present invention and simplified description, rather than It is to be understood that the device or elements referred to have a particular orientation, are constructed and operated in a particular orientation and are therefore not to be construed as limiting. Moreover, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implied number of technical features indicated. Thus, the defined "first", "second" features may include one or more of the features, either explicitly or implicitly. In the description of the present invention, "a plurality" means two or more unless otherwise stated.

In the description of the present invention, it should be noted that the terms "mounting" and "connecting" are to be understood broadly, and may be, for example, a fixed connection, a detachable connection, or an integral, unless otherwise explicitly stated and defined. Ground connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be said that the internal connection of the two elements. The specific meaning of the above terms in the present invention can be understood in the specific circumstances by those skilled in the art.

The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

Example 1

The invention relates to an inverter air conditioner control method. The method is applied to an inverter air conditioner controller, and the rated input voltage is 220Vac, 50Hz, and the rated busbar working current is 8A. As shown in FIG. 1, the controller includes a main control MCU8, a rectification and a PFC unit. Circuit 1, three-phase inverter circuit 6, AC voltage detecting unit 2 connected to main control MCU8 and main circuit bus DC voltage detecting circuit 4, main control MCU8 connected with compressor phase current iU/iV detection The signal is measured, the master MCU drives the three-phase inverter circuit through the inverter drive circuit 5, and drives the PFC unit through the PFC drive circuit 7, and the energy storage is connected between the rectifier and the PFC unit circuit 1 and the three-phase inverter circuit 6. Capacitor C2; the method includes:

The q-axis current in the compressor is compensated and controlled. The compensation mode is: update the q-axis current command value according to the main circuit bus voltage Vp and participate in the traditional FOC vector algorithm, and increase the q-axis current command value when Vp rises, and adjust the V-axis current command value when Vp rises. Low q-axis current command value. .

The control principle of the algorithm of the present invention is shown in FIG. 2. In the present invention, the main circuit bus voltage detecting circuit detects the main circuit bus voltage Vp, and then updates the command value of the q-axis current according to Vp, thereby completing the q-axis current. Compensation, increase the q-axis current command value when Vp rises, and lower the q-axis current command value when Vp falls, so that Vp and q-axis current command value are matched, so that the output is higher at a higher voltage in half of the power frequency cycle. High electrical power, lower output power at lower voltages, significantly reducing the need for storage capacitor capacity, increasing the power density of the controller, reducing the size of the controller, and thus reducing costs.

In a specific implementation process, the compensation mode is specifically: generating a modulation coefficient Mv according to the main circuit bus voltage Vp, and multiplying the Mv by the q-axis current command value as a new q-axis current command value to participate in the conventional FOC vector algorithm.

The two types with more practical value are listed as follows:

In this embodiment, a strong compensation control is performed, and N=1, that is, Mv=Vp/V_p, the sampling interval of the DC voltage Vp of the main circuit bus is 1 mS, and 200 sampling periods are included in 0.2 seconds, including 200 Vp samples. The value is averaged over the last 200 Vp samples to get the V_p value.

The invention obtains the instantaneous voltage value Vp of the bus voltage by detecting the DC voltage Vp value of the main circuit bus, and averages Vp in a period T to obtain an average value V_p, where T is a continuous T time before the current adoption period. Segment, through the ratio of Vp / V_p, can get the fluctuation ratio of the bus DC voltage, The voltage fluctuation ratio is used as a compensation parameter to compensate the iq current. In the d_q rotating coordinate system, the q-axis current is used for work. Therefore, the compensation can output a large power and fluctuate when the voltage fluctuation ratio is high. When compared, the output power becomes smaller.

In a specific implementation process, the method further includes performing a field weakening control on the compressor, specifically:

The idref is adjusted according to the main circuit bus voltage Vp, and the idref value is adjusted when i _q and i _d satisfy the following formula, otherwise the idref value is controlled according to the non-compensation method:

(L _q ×i _q ) ² +(L _d ×i _d +ψ) ² =(Vp-k) ² /(3×ω ² )

Where k is a reserved deviation voltage value, which is a constant greater than zero and less than the minimum value of Vp, this embodiment takes k=10;

(L _q ×i _q ) ² +(L _d ×i _d +ψ) ² ≤(Vp-k) ² /(3×ω ² )

Where Ld is the d-axis inductance, Lq is the q-axis inductance, ω is the compressor speed, ψ is the compressor rotor flux, i _d is the d-axis current of the compressor, i _q is the q-axis current of the compressor, and idref is The d-axis current command value of the compressor. In this embodiment, the reserved deviation voltage value k=10 is preferred. Due to the introduction of the k value, the Vp value is converted into Vp-k during the calculation, thereby avoiding the detection error due to the Vp value, so that the controller should enter the weak magnetic control. There is no entry into the weak magnetic control.

In a specific implementation process, the capacitance of the storage capacitor C2 of the embodiment satisfies the value of less than 0.5 μF/W and the maximum allowable output power of the inverter air conditioner controller, taking as small a value as possible, taking into account the conventional capacitor. Capacitance, the preferred value of C2 in this embodiment is 470 μF, and a 3 μF film capacitor is connected in parallel, which is much smaller than the capacitance of the electrolytic capacitor used in the current general technology. By using the q-axis current for compensation control and using a small storage capacitor, on the one hand, the effective volume of the controller can be significantly reduced, the cost of the controller can be reduced, the power density of the controller can be increased, and more importantly, the compensation can be controlled. Cooperating, the bus ripple voltage on the storage capacitor does not rise significantly when the capacity of the storage capacitor is reduced, and the rise of the bus ripple voltage is reduced.

Preferably, in a specific implementation process, a rectifying resistor R1 is connected in series with the inductor branch in the PFC unit circuit of the PFC unit circuit 1. Since the inductor exists in the PFC circuit, and the compressor is a load with inductive characteristics, an unstable oscillating circuit structure is formed when combined with the storage capacitor. By setting the damper circuit, the oscillating amplitude can be effectively reduced, and the stability of the controller is provided. .

In a specific implementation process, the resistance of the damping resistor R1 is greater than or equal to 0.1 ohm, which is in this embodiment. For the convenience of production, the resistance value is integrated into the reactor L1, and the resistance of R1 is 0.2 Ω.

The invention controls the output power of the inverter air conditioner controller by the compensation control mode, reduces the energy storage function of the energy storage capacitor, can effectively reduce the demand for the storage capacitor, improve the power density of the controller, reduce the volume of the controller, and reduce The capacity of the electrolytic capacitor, which in turn reduces costs.

Example 2

This embodiment is improved on the basis of Embodiment 1. As shown in FIG. 2, the main control MCU 8 detects the main circuit bus current through the main circuit bus current detecting circuit 3, and the main circuit bus current io also participates in the compensation control of the q-axis current. Specifically, the modulation coefficient Mv is further transformed into Mv′, where the modulation coefficient Mv′=(Mv−1)×(iorms/I)+1, where I is a constant, and in this embodiment, I is the rated operating current of the main circuit busbar. The effective value, that is, I=8, so Mv'=(Mv-1)×(iorms/8)+1, iorms is the effective value of the main circuit bus current io.

In the embodiment, when the controller performs the compensation control, the output power is small when the controller is running at a low frequency. At this time, the energy storage effect of the electrolytic capacitor is relatively good, so the compensation amount can be appropriately reduced at this time, and the main circuit bus current io at this time. The effective value is less than the rated value of the rated working current of the main circuit bus, iorms/8<1, the compensation of the q-axis current is reduced, and the q-axis current is matched with the lower operating frequency, which can effectively improve the compressor noise problem during low-frequency operation. Therefore, by changing the Mv value, the amount of compensation can be reduced, and the compressor noise problem at low frequency operation can be improved.

Example 3

This embodiment is improved on the basis of Embodiment 1. As shown in FIG. 3, in order to improve the adjustment performance of the PFC, a dual PFC is used, and the driving signals of the two PFCs are 180 degrees out of phase, the circuit parameters are completely the same, and the inductance L1 The DC resistance Rs with L2 is ≥ 0.5 Ω.

The same or similar reference numerals correspond to the same or similar parts;

The positional relationship is described in the drawings for illustrative purposes only and is not to be construed as limiting the invention;

It is apparent that the above-described embodiments of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Other variations or modifications of the various forms may be made by those skilled in the art in light of the above description. There is no need and no way to exhaust all of the implementations. Any modifications, equivalent substitutions and improvements made within the spirit and scope of the invention are intended to be included within the scope of the appended claims.

Claims

An inverter air conditioner control method, the method is applied to an inverter air conditioner controller, wherein the controller comprises a main control MCU, a rectification and PFC unit circuit, a three-phase inverter circuit, an AC voltage detecting unit connected to the main control MCU, and The main circuit bus voltage detection circuit, the main control MCU is connected with the compressor phase current iU/iV detection signal, the main control MCU drives the three-phase inverter circuit through the inverter drive circuit and drives the PFC unit through the PFC drive circuit, in the rectification and A storage capacitor C is connected between the PFC unit circuit and the three-phase inverter circuit; and the method includes:

The q-axis current in the compressor is compensated and controlled. The compensation mode is: update the q-axis current command value according to the main circuit bus voltage Vp to participate in the traditional FOC vector algorithm, increase the q-axis current command value when Vp rises, and decrease when Vp decreases. Q axis current command value.
The inverter air conditioner control method according to claim 1, wherein the compensation mode is specifically: generating a modulation coefficient Mv according to the main circuit bus voltage Vp, and multiplying the Mv by the q-axis current command value as a new q-axis. Current command values and participate in traditional FOC vector algorithms.
The inverter air conditioner control method according to claim 2, wherein the specific method of generating a modulation coefficient Mv according to the main circuit bus voltage Vp is:

The function f(Vp/V_p) with Vp/V_p as an independent variable is constructed such that the modulation coefficient Mv=f(Vp/V_p), V_p is the average value of the main circuit bus voltage Vp in a long period T time.
The inverter air conditioner control method according to claim 3, characterized in that: when weak compensation is used, the modulation coefficient Mv = (Vp / V_p) 1 / N , wherein N = 2 or 3, V_p is the main circuit bus voltage The average value of Vp over a long period of time T;

When strong compensation is used, the modulation factor Mv = (Vp / V_p) N , where N = 1 or 2, V_p is the average value of the main circuit bus voltage Vp over a long period T time.
The inverter air conditioner control method according to any one of claims 1 to 4, wherein the method further comprises performing a field weakening control on the compressor, specifically:

The idref is set according to the main circuit bus voltage Vp, and the idref value is adjusted when i q and i d satisfy the following formula, otherwise the idref value is controlled according to the non-compensation method:

(Lq×i q ) 2 +(Ld×i d +ψ) 2 =(Vp-k) 2 /(3×ω 2 )

Where k is a constant greater than zero and less than Vp;

And when the idref value is adjusted, i q , i d must meet the following conditions:

(Lq×i q ) 2 +(Ld×i d +ψ) 2 ≤(Vp-k) 2 /(3×ω 2 )

Where Ld is the d-axis inductance, Lq is the q-axis inductance, ω is the compressor speed, ψ is the compressor rotor flux, i d is the d-axis current of the compressor, i q is the q-axis current of the compressor, and idref is The d-axis current command value of the compressor.
The inverter air conditioner controller according to any one of claims 1 to 4, wherein the method further comprises: acquiring a main circuit bus current io, and using the main circuit bus current io to participate in the compensation control of the q-axis current, specifically To further transform the modulation factor Mv into Mv', where the modulation factor Mv' = (Mv - 1) x (iorms / I) + 1, where I is a constant, iorms is the effective value of the main circuit bus current io.
The inverter air conditioner control method according to claim 1, wherein the capacitance of the storage capacitor C is less than a product of 0.5 μF/W and a maximum allowable output power of the inverter air conditioner controller.
The inverter air conditioner control method according to claim 1, wherein the rectifying and inductive branch in the PFC unit circuit of the PFC unit circuit has a damping resistor in series.
The inverter air conditioner control method according to claim 8, wherein the resistance of the damping resistor is greater than or equal to 0.1 ohm.