CN104034958B - Inverter Weight detector and method thereof based on virtual impedance - Google Patents

Abstract

The invention discloses a kind of inverter Weight detector based on virtual impedance, including an inverter, an output voltage sampling circuit, an inductive current sample circuit, a virtual impedance circuit, an operational amplifier, a CPU processor. A kind of inverter load detection method based on virtual impedance, adopt virtual impedance, with output voltage, inductive current is compensated, indirectly obtain inverter output load current, thus eliminating the harmonic wave impact on compensation precision, especially, when nonlinear load, the accuracy of detection of inverter output loading power current is high. This technology overcomes when output harmonic wave content height, the shortcoming that existing electric capacity Non Power Compensation Process accuracy of detection is not high.

Description

Inverter Weight detector and method thereof based on virtual impedance

Technical field

The present invention relates to inverter Weight detector and method thereof, be based especially on inverter Weight detector and the method thereof of virtual impedance.

Background technology

In inverter, in order to ensure closed-loop stabilization, adaptive load ability width, power tube protection is reliable, generally all can add inductor current feedback; Simultaneously in order to show output loading power in real time, it is to avoid inverter transships or crosses cause thermal damage, bearing power detection and overload protection also can be added.

In prior art some inverters in order to proof load power detection enough accurate, shown in Figure 1, two current measuring elements can be adopted respectively inductive current and output load current to be detected, but so necessarily cause cost increase, circuit structure also can be made to complicate.

Output load current detecting element in order to reduce cost, is then saved by other inverters. In order to reduce the impact of output filter capacitor, it is necessary to inductance output is carried out reactive-load compensation. Generally adopt techniques below method: suppose that output voltage is sine wave, first calculate the idle component in output capacitance, then this this part idle component is superimposed in the load capacity calculated with inductive current, indirectly obtains output data. But, there is harmonic wave in inverter output voltage, can produce certain higher hamonic wave and idle on output filter capacitor, and above-mentioned technology way is difficult to eliminate this kind of impact. Especially, when the load of inverter is nonlinear load (such as RCD load), output harmonic wave content is high, and filter capacitor reactive power is big, it is difficult to higher hamonic wave is compensated, and compensation precision is not high, output loading accuracy of detection is poor.

Therefore can improving inverter output loading accuracy of detection height, to save again cost be this area technical problem urgently to be resolved hurrily.

Summary of the invention

One purpose of the present invention is to provide a kind of inverter Weight detector based on virtual impedance, can improve inverter output loading accuracy of detection high, can save again cost.

A kind of inverter Weight detector based on virtual impedance, it is characterised in that including a: inverter module, an inductive current sample circuit, an output voltage sampling circuit, a virtual impedance circuit, an operational amplifier, a CPU processor; Described inverter module includes DC/AC module and filter circuit, and described filter circuit includes an a filter inductance L and filter capacitor C, and filter circuit connects described DC/AC module output two ends; Described output voltage sampling circuit input termination inverter module, the output of described output voltage sampling circuit connects described virtual impedance circuit input end; The output of described virtual impedance circuit connects the negative input end of described operational amplifier; Described inductive current sample circuit input termination inverter module, the output of described inductive current sample circuit connects the positive input terminal of described operational amplifier; The outfan of described operational amplifier is connected to described CPU processor, described CPU processor output inverter output current value i_O。

In an embodiment of the present invention, described output voltage sampling circuit is by the instantaneous voltage value u of filter capacitor C and filter inductance L intersection_invDecay K_usTimes, described output voltage sampling circuit output end voltage value u'_inv, namelyWherein K_us> 0, the output of described output voltage sampling circuit connects virtual impedance circuit.

In an embodiment of the present invention, described inductive current sample circuit includes a current sensor and one first sampling resistor R_S1; The secondary of described current sensor described first sampling resistor R in parallel_S1, the outfan of described inductive current sample circuit is connected to the positive input terminal of operational amplifier. Described current sensor will flow through the current value i of filter inductance L_LDecay K_isTimes, described inductive current sample circuit output voltage values u_Rs1, namely

In an embodiment of the present invention, described virtual impedance circuit includes sampling capacitor C_S, the second sample resistance R_S2; Described sampling capacitor C_SAn end be connected to the outfan of described output voltage sampling circuit, described sampling capacitor C_SThe other end be connected to described second sampling resistor R_S2One end, described operational amplifier negative input end; Described second sampling resistor R_S2Other end ground connection. Described sampling capacitor C_SCapacitance be filter capacitor C'sTimes, namelyDescribed virtual impedance circuit output voltage value is u_Rs2, namely $u_{\mathrm{Rs}2}=R_{S2}\·i_{\mathrm{CS}}=R_{S2}\·\mathrm{Cs}\frac{d({u^{\′}}_{\mathrm{inv}}-u_{\mathrm{Rs}2})}{\mathrm{dt}}\≈R_{S2}\·\mathrm{Cs}\frac{d{u^{\′}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·C\frac{{\mathrm{du}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C,$ It is wherein i_CThe current value of filter capacitor, i_CSCurrent value for sampling capacitor. Wherein said sampling capacitor C_SThe value the second sample resistance R more than 100 times_S2Value.

In an embodiment of the present invention, the input voltage value u of the positive input terminal of described operational amplifier⁺, namelyWherein u_Rs1For inductive current sample circuit output voltage values, the input voltage value of the negative input end of described operational amplifier is u^-, namelyWherein u_Rs2For virtual impedance circuit output voltage value; The output voltage values of the output end voltage value of inductive current sample circuit Yu described virtual impedance circuit is asked difference to obtain output voltage values u1 by described operational amplifier, namely $u1=u^{+}-u^{-}=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C;$ Wherein i_CFor flowing through the current value of filter capacitor, $\frac{R_{S1}}{K_{\mathrm{is}}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}=K_O,$ K_O> 0, then $u1=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C=K_O\·(i_L-i_C)=K_O\·i_O.$ The output of described amplifier connects described CPU processor input, and described CPU processor calculates the output current value of also output inverter

It is a further object of the present invention to provide a kind of inverter load detection method based on virtual impedance, it is achieved the detection to inverter output load current.It is characterized in that: realize step and include:

Step 1: output voltage sampling circuit obtains instantaneous voltage value u' in real time_inv, utilize formulaCalculate the instantaneous voltage value u of filter capacitor and filter inductance intersection_inv, i.e. the output instantaneous voltage value u of inverter_inv=K_us·u'_inv, wherein K_usFor voltage sampling circuit to u_invAttenuation multiple;

Step 2: inductive current sample circuit obtains the first sampling resistor R in real time_S1Magnitude of voltage u_Rs1, whereinWherein i_LFor the current value of filter inductance, i'_LFor current transformer output current value, K_isFor current transformer to inductor current value i_LAttenuation multiple;

Step 3: virtual impedance circuit obtains the second sampling resistor R in real time_S2On magnitude of voltage u_Rs2, wherein $u_{\mathrm{Rs}2}=R_{S2}\·i_{\mathrm{CS}}=R_{S2}\·\mathrm{Cs}\frac{d({u^{\′}}_{\mathrm{inv}}-u_{\mathrm{Rs}2})}{\mathrm{dt}}\≈R_{S2}\·\mathrm{Cs}\frac{d{u^{\′}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·C\frac{{\mathrm{du}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C,$ Wherein i_CFor the current value of filter capacitor, i_CSFor the current value of sampling capacitor,For sampling capacitor C_SThe ratio of capacitance and filter capacitor C capacitance.

Step 4: operational amplifier obtains its output voltage values u1 in real time, the input voltage value u of positive input terminal⁺, the input voltage value of negative input end is u^-, i.e. u1=u⁺-u^-=u_Rs1-u_Rs2;

Step 5: according to formula $u1=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C=K_O\·(i_L-i_C)=K_O\·i_O.$ Calculate output electric current $i_O=\frac{u1}{K_O},$ Wherein $\frac{R_{S1}}{K_{\mathrm{is}}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}=K_O;$

According to inverter output current value i_O, inverter output instantaneous voltage value u_inv, utilize formulaCalculate the bearing power value S of inverter.

Compared with prior art, the present invention has the beneficial effect that:

1, the inverter Weight detector of the present invention, it is only necessary to utilize the current sensor of the detection inductive current of inverter self, it is not necessary to be further added by extra current sensor, possess simple in construction, be substantially reduced the feature of cost.

2, the inverter load detection method of the present invention, adopt virtual impedance, with output voltage inductive current compensated and indirectly obtain output load current, eliminate the harmonic wave impact on compensation precision, especially, when nonlinear load, the accuracy of detection of inverter output loading power is high. This technology overcomes when output harmonic wave content height, the shortcoming that existing electric capacity Non Power Compensation Process accuracy of detection is not high.

Accompanying drawing explanation

Fig. 1 is a kind of inverter load detecting theory diagram in prior art;

Fig. 2 is the inverter load detecting schematic diagram based on virtual impedance of the present invention.

Detailed description of the invention

Below in conjunction with drawings and Examples, the present invention will be further described.

The present embodiment provides a kind of inverter Weight detector based on virtual impedance, it is characterized in that, including: an inverter module, an inductive current sample circuit, an output voltage sampling circuit, a virtual impedance circuit, an operational amplifier, a CPU processor; Described inverter module includes DC/AC module and filter circuit, and described filter circuit includes an a filter inductance L and filter capacitor C, and filter circuit connects described DC/AC module output two ends; Described output voltage sampling circuit input termination inverter module, the output of described output voltage sampling circuit connects described virtual impedance circuit input end; The output of described virtual impedance circuit connects the negative input end of described operational amplifier; Described inductive current sample circuit input termination inverter module, the output of described inductive current sample circuit connects the positive input terminal of described operational amplifier; The outfan of described operational amplifier is connected to described CPU processor, described CPU processor output inverter output current value i_O. Concrete schematic diagram is referring to Fig. 2.

Inverter module includes DC/AC module, the filter circuit being made up of filter inductance L and filter capacitor C. One end of DC/AC module outfan is connected to one end of filter inductance L, and the other end of described filter inductance L is connected to one end of filter capacitor C, the other end of filter capacitor C is connected to the other end of described DC/AC module outfan.

Described output voltage sampling circuit is by the instantaneous voltage value u of filter capacitor C and filter inductance L intersection_invDecay K_usTimes, described output voltage sampling circuit output end voltage value u'_inv, namelyWherein K_us> 0;

Described inductive current sample circuit includes a current sensor and one first sampling resistor R_S1Constituting, described current sensor will flow through the current value i of filter inductance_LDecay K_isTimes, the secondary of described current sensor described first sampling resistor R in parallel_S1, described inductive current sample circuit output voltage values u_Rs1, namely

Described virtual impedance circuit includes sampling capacitor C_S, the second sample resistance R_S2, described sampling capacitor C_SThe resistance the second sample resistance R more than 100 times_S2Resistance.

The outfan of described output voltage sampling circuit is connected to sampling capacitor C_SOne end, CPU processor input, sampling capacitor C_SThe other end be connected to the second sampling resistor R_S2One end, operational amplifier negative input end, the second sampling resistor R_S2Other end ground connection.

Described sampling capacitor C_SCapacitance be filter capacitor C'sTimes, namelyDescribed virtual impedance circuit output voltage value is u_Rs2, namely $u_{\mathrm{Rs}2}=R_{S2}\·i_{\mathrm{CS}}=R_{S2}\·\mathrm{Cs}\frac{d({u^{\′}}_{\mathrm{inv}}-u_{\mathrm{Rs}2})}{\mathrm{dt}}\≈R_{S2}\·\mathrm{Cs}\frac{d{u^{\′}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·C\frac{{\mathrm{du}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C;$

The input voltage value u of the positive input terminal of described operational amplifier⁺, namelyThe input voltage value of the negative input end of described operational amplifier is u^-, namely $u^{-}=u_{\mathrm{Rs}2}=R_{S2}\·i_{\mathrm{CS}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C,$

The output voltage values of the output end voltage value of inductive current sample circuit Yu described virtual impedance circuit is asked difference to obtain output voltage values u1 by described operational amplifier, namely $u1=u^{+}-u^{-}=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C;$ Wherein $\frac{R_{S1}}{K_{\mathrm{is}}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}=K_O,$ K_O> 0, then $u1=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C=K_O\·(i_L-i_C)=K_O\·i_O,$ Described CPU processor is for calculating the output instantaneous voltage value u of inverter_inv=u'_inv×K_us; Described CPU processor is for calculating the output current value of inverterWherein i_CFor flowing through the current value of filter capacitor.

The present embodiment provides a kind of inverter load detection method based on virtual impedance, implements step as follows:

Step 1: output voltage sampling circuit obtains instantaneous voltage value u' in real time_inv, utilize formulaCalculate the instantaneous voltage value u of filter capacitor and filter inductance intersection_inv, i.e. the output instantaneous voltage value u of inverter_inv=K_us·u'_inv, wherein K_usFor voltage sampling circuit to u_invAttenuation multiple;

Step 2: inductive current sample circuit obtains the first sampling resistor R in real time_S1Magnitude of voltage u_Rs1, whereinWherein i_LFor the current value of filter inductance, i'_LFor current transformer output current value, K_isFor current transformer to inductor current value i_LAttenuation multiple;

Step 3: virtual impedance circuit obtains the second sampling resistor R in real time_S2On magnitude of voltage u_Rs2, wherein $u_{\mathrm{Rs}2}=R_{S2}\·i_{\mathrm{CS}}=R_{S2}\·\mathrm{Cs}\frac{d({u^{\′}}_{\mathrm{inv}}-u_{\mathrm{Rs}2})}{\mathrm{dt}}\≈R_{S2}\·\mathrm{Cs}\frac{d{u^{\′}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·C\frac{{\mathrm{du}}_{\mathrm{inv}}}{\mathrm{dt}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C,$ Wherein i_CFor the current value of filter capacitor, i_CSFor the current value of sampling capacitor,For sampling capacitor C_SThe ratio of capacitance and filter capacitor C.

Step 4: operational amplifier obtains its output voltage values u1 in real time, the input voltage value u of positive input terminal⁺, the input voltage value of negative input end is u^-, i.e. u1=u⁺-u^-=u_Rs1-u_Rs2;

Step 5: according to formula $u1=\frac{R_{S1}}{K_{\mathrm{is}}}\·i_L-\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}\·i_C=K_O\·(i_L-i_C)=K_O\·i_O,$ Calculate output electric current $i_O=\frac{u1}{K_O},$ Wherein $\frac{R_{S1}}{K_{\mathrm{is}}}=\frac{R_{S2}}{K_{\mathrm{ic}}\·K_{\mathrm{us}}}=K_O;$

According to inverter output current value i_O, inverter output instantaneous voltage value u_inv, utilize formulaCalculate the bearing power value S of inverter.

The present invention not only applies and single-phase inverter, it is also possible to application and three-phase inverter, as long as obtaining the output power value of each phase in three-phase inverter is applied respectively, and the output power value of cumulative acquisition system.

Above-listed preferred embodiment; the object, technical solutions and advantages of the present invention have been further described; it is it should be understood that; the foregoing is only presently preferred embodiments of the present invention; not in order to limit the present invention; all within the spirit and principles in the present invention, any amendment of making, equivalent replacement, improvement etc., should be included within protection scope of the present invention.

Claims (8)

1. the inverter Weight detector based on virtual impedance, it is characterised in that including a: inverter module, an inductive current sample circuit, an output voltage sampling circuit, a virtual impedance circuit, an operational amplifier, a CPU processor;

Described inverter module includes DC/AC module and filter circuit, and described filter circuit includes an a filter inductance L and filter capacitor C, and filter circuit connects described DC/AC module output two ends; Described output voltage sampling circuit input termination inverter module, the output of described output voltage sampling circuit connects described virtual impedance circuit input end; The output of described virtual impedance circuit connects the negative input end of described operational amplifier; Described inductive current sample circuit input termination inverter module, the output of described inductive current sample circuit connects the positive input terminal of described operational amplifier; The outfan of described operational amplifier is connected to described CPU processor, described CPU processor output inverter output current value i_O;

Described inductive current sample circuit includes a current sensor and one first sampling resistor R_S1; The secondary described first sampling resistor R of series connection of described current sensor_S1, the outfan of described inductive current sample circuit is connected to the positive input terminal of operational amplifier;

Described virtual impedance circuit includes sampling capacitor C_S, the second sampling resistor R_S2; Described sampling capacitor C_SAn end be connected to the outfan of described output voltage sampling circuit, described sampling capacitor C_SThe other end be connected to described second sampling resistor R_S2One end, described operational amplifier negative input end; Described second sampling resistor R_S2Other end ground connection.

2. the inverter Weight detector based on virtual impedance according to claim 1, it is characterised in that: described output voltage sampling circuit is by the instantaneous voltage value u of filter capacitor C and filter inductance L intersection_invDecay K_usTimes, described output voltage sampling circuit output end voltage value u'_inv, namelyWherein K_us> 0, the output of described output voltage sampling circuit connects virtual impedance circuit.

3. the inverter Weight detector based on virtual impedance according to claim 2, it is characterised in that: described current sensor will flow through the current value i of filter inductance L_LDecay K_isTimes, described inductive current sample circuit output voltage values u_Rs1, namely

4. the inverter Weight detector based on virtual impedance according to claim 3, it is characterised in that: described sampling capacitor C_SCapacitance be filter capacitor C'sTimes, namelyDescribed virtual impedance circuit output voltage value is u_Rs2, namelyWherein i_CFor filter capacitor current value, i_CSCurrent value for sampling capacitor.

5. the inverter Weight detector based on virtual impedance according to claim 1, it is characterised in that: described sampling capacitor C_SThe value the second sampling resistor R more than 100 times_S2Resistance.

6. the inverter Weight detector based on virtual impedance according to claim 4, it is characterised in that: the input voltage value u of the positive input terminal of described operational amplifier⁺, namelyWherein u_Rs1For inductive current sample circuit output voltage values, the input voltage value of the negative input end of described operational amplifier is u^-, namelyWherein u_Rs2For virtual impedance circuit output voltage value;

The output voltage values of the output end voltage value of inductive current sample circuit Yu described virtual impedance circuit is asked difference to obtain output voltage values u1 by described operational amplifier, namely

Wherein i_CFor flowing through the current value of filter capacitor,K_O> 0, K_OFor operational amplifier amplification;Then

7. the inverter Weight detector based on virtual impedance according to claim 6, it is characterised in that:

The output of described amplifier connects the input of described CPU processor, and described CPU processor calculates the output current value of also output inverter

8. the inverter load detection method based on virtual impedance, it is characterised in that: realize step and include:

Step 1: output voltage sampling circuit obtains instantaneous voltage value u' in real time_inv, utilize formulaCalculate the instantaneous voltage value u of filter capacitor and filter inductance intersection_inv, i.e. the output instantaneous voltage value u of inverter_inv=K_us·u'_inv, wherein K_usFor voltage sampling circuit to u_invAttenuation multiple;

Step 2: inductive current sample circuit obtains the first sampling resistor R in real time_S1Magnitude of voltage u_Rs1, whereinWherein i_LFor the current value of filter inductance, i '_LFor current transformer output current value, K_isFor current transformer to inductor current value i_LAttenuation multiple;

Step 3: virtual impedance circuit obtains the second sampling resistor R in real time_S2On magnitude of voltage u_Rs2, wherein, wherein i_CFor the current value of filter capacitor, i_CSFor the current value of sampling capacitor,For sampling capacitor C_SThe multiple that capacitance is filter capacitor C;

Step 4: operational amplifier obtains its output voltage values u1 in real time, the input voltage value u of positive input terminal⁺, the input voltage value of negative input end is u^-, i.e. u1=u⁺-u^-=u_Rs1-u_Rs2;

Step 5: according to formulaCalculate output electric currentWhereinK_OFor operational amplifier amplification;

Step 6: according to inverter output current value i_O, inverter output instantaneous voltage value u_inv, utilize formulaCalculate the bearing power value S of inverter.