CN103001511B - Voltage converter and operating method thereof - Google Patents

Voltage converter and operating method thereof Download PDF

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Publication number
CN103001511B
CN103001511B CN201110269870.5A CN201110269870A CN103001511B CN 103001511 B CN103001511 B CN 103001511B CN 201110269870 A CN201110269870 A CN 201110269870A CN 103001511 B CN103001511 B CN 103001511B
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voltage
switching device
circuit
diode
inductance
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CN103001511A (en
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耿后来
倪华
梅晓东
胡兵
赵为
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Sungrow Power Supply Co Ltd
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Sungrow Power Supply Co Ltd
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Abstract

The invention discloses a voltage converter which is used for converting direct-current voltage output by a direct-current power supply into alternating voltage provided for an alternating-current load. The voltage converter comprises a bypass unit, a boosted circuit, a first energy-storage filtering unit, a voltage-reduction circuit and an inverter circuit. The boosted circuit, the first energy-storage filtering unit, the voltage-reduction circuit and the inverter circuit are sequentially parallelly connected between the direct-current power supply and the alternating-current load. The bypass unit is used for bypassing the boosted circuit when the direct-current voltage is not smaller than the absolute value of an instantaneous value of the power grid voltage. The inverter circuit actuates at power frequency in each work cycle of the alternating-current voltage. The booster circuit operates only when the direct-current voltage is smaller than the absolute value of instantaneous value of the power grid voltage. Compared with the prior art, the voltage converter is wide in direct-current voltage working range, high in converting efficiency and low in cost.

Description

A kind of voltage changer and operation method thereof
Technical field
The invention belongs to field of power electronics, be specifically related to the voltage changer of converting direct-current voltage into alternating-current voltage and operation method thereof.
Background technology
Along with the exhaustion day by day of the energy, renewable energy power generation technology, as photovoltaic generation and wind power generation etc., obtain extensive concern, the electric energy of the instability wherein regenerative resource sent converts stable AC energy to, and to be supplied to the device of AC load or AC network particularly important, the various operating modes that input voltage changes in a big way must be adapted to, realize the efficient conversion of energy simultaneously.
With regard to photovoltaic DC-to-AC converter, isolated form and non-isolation type can be divided into.Wherein, the attention rate that is subject to of the non-isolation type inverter of the high and low cost of efficiency is the highest.Conventional non-isolation type inverter, adopts prime DC/DC booster circuit to realize the adjustment of direct voltage, and adopt rear class full-bridge circuit to realize inversion, front and back stages circuit is all operated in high frequency state, and switching loss is higher, and conversion efficiency is low; Further, the switching device of front and back stages circuit need select high speed switch tube, and cost is high.
Summary of the invention
In view of this, the object of the embodiment of the present invention is to provide relative to prior art, the voltage changer that conversion efficiency is high, cost is low and operation method thereof.
A kind of voltage changer that the embodiment of the present invention provides, is supplied to AC load for converting direct-current voltage into alternating-current voltage DC power supply exported, and comprises booster circuit, the first energy storage filter unit, reduction voltage circuit, inverter circuit and by-pass unit; The input of described booster circuit is connected in the two ends of DC power supply in parallel, between the output that described first energy storage filter unit, reduction voltage circuit and inverter circuit order is connected in described booster circuit in parallel and AC load, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit; The direct voltage that described booster circuit is used for DC power supply exports is converted to higher direct voltage and exports; Described first energy storage filter unit is used for the high fdrequency component in the higher direct voltage that described in filtering, booster circuit exports and generates the first intermediate voltage exporting; Described first intermediate voltage is converted to the absolute value voltage of sine wave AC voltage by described reduction voltage circuit; The absolute value voltage of the sine wave AC voltage that described reduction voltage circuit exports by inverter circuit carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load; Described by-pass unit is used for during described direct voltage is not less than the absolute value of line voltage instantaneous value, by described booster circuit bypass.
According to above-mentioned voltage changer, when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit just works, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work, and therefore conversion efficiency is improved.
Preferably, the by-pass unit in above-mentioned voltage changer is the first diode, and the anode of described first diode connects the positive pole of DC power supply, and the negative electrode of described first diode connects the output of booster circuit.
Further, above-mentioned booster circuit comprises the first inductance, the second diode, the first switching device, the described first end of the first inductance is connected with the positive pole of DC power supply, second end of the first inductance is connected with the first end of the first switching device with the anode of the second diode, the negative pole of the second termination DC power supply of the first switching device, the negative electrode of the second diode connects the second end of described by-pass unit; Above-mentioned inverter circuit comprises the 4th switching device, the 5th switching device, the 6th switching device and the 7th switching device, 4th switching device and the 5th switching device are connected in series formation first branch road, 6th switching device and the 7th switching device are connected in series formation second branch road, first branch road and the second branch road are connected in parallel on the output of reduction voltage circuit respectively, the tie point of the 4th switching device and the 5th switching device draws the first end connecing AC load, and the tie point of the 6th switching device and the 7th switching device draws the second end connecing AC load.
Further, above-mentioned first energy storage filter unit comprises the first electric capacity, the negative electrode of the first termination second diode of the first electric capacity, the negative pole of the second termination DC power supply of the first electric capacity; Above-mentioned reduction voltage circuit comprises a buck circuit, one buck circuit comprises second switch device, the 3rd diode, the second inductance, the first end of second switch device is connected with the first end of the first electric capacity, second end of second switch device is connected with the first end of the second inductance with the negative electrode of the 3rd diode, the anode of the 3rd diode connects the second end of the first electric capacity, and the second end of the second inductance is connected with inverter circuit.
Further, above-mentioned reduction voltage circuit also comprises the 2nd buck circuit, 2nd buck circuit comprises the 3rd switching device, the 3rd inductance, second end of the first termination first electric capacity of the 3rd switching device, second termination of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 3rd diode, and the second end of the 3rd inductance is connected with inverter circuit.
Preferably, above-mentioned second switch device and the 3rd switching device, the second inductance and the 3rd inductance are respectively the electronic devices and components of same model.
Further, above-mentioned first energy storage filter unit also comprises the second electric capacity be connected with the first capacitances in series, second end of the first electric capacity is connected with the first end of the second electric capacity and tie point is used for producing the midpoint potential of described first intermediate voltage, the negative pole of the second termination DC power supply of the second electric capacity; Described 2nd buck circuit also comprises the 4th diode, second end of the first termination second electric capacity of the 3rd switching device, second termination of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 4th diode, and the negative electrode of the 4th diode is connected with the anode of the 3rd diode and tie point connects the midpoint potential of described first intermediate voltage.
Preferably, above-mentioned first electric capacity and the second electric capacity, second switch device and the 3rd switching device, the 3rd diode and the 4th diode, the second inductance and the 3rd inductance are respectively the electronic devices and components of same model.
Further, above-mentioned voltage changer also comprises the second energy storage filter unit be connected between reduction voltage circuit and inverter circuit, and the high fdrequency component in the absolute value voltage of the sine wave AC voltage exported for reduction voltage circuit described in filtering also generates the second intermediate voltage and exports to inverter circuit.
According to above-mentioned voltage changer, when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work, and therefore conversion efficiency is improved.
The embodiment of the present invention additionally provides a kind of operation method of voltage changer, the converting direct-current voltage into alternating-current voltage that described voltage changer is used for DC power supply exports is supplied to AC load, comprises booster circuit, the first energy storage filter unit, reduction voltage circuit, inverter circuit and by-pass unit; The input of described booster circuit is connected in the two ends of DC power supply in parallel, between the output that described first energy storage filter unit, reduction voltage circuit and inverter circuit order is connected in described booster circuit in parallel and AC load, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit; The direct voltage that described booster circuit is used for DC power supply exports is converted to higher direct voltage and exports; Described first energy storage filter unit is used for the high fdrequency component in the higher direct voltage that described in filtering, booster circuit exports and generates the first intermediate voltage exporting; Described first intermediate voltage is converted to the absolute value voltage of sine wave AC voltage by described reduction voltage circuit; The absolute value voltage of the sine wave AC voltage that described reduction voltage circuit exports by inverter circuit carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load; Described by-pass unit is used for during described direct voltage is not less than the absolute value of line voltage instantaneous value, by described booster circuit bypass; Booster circuit comprises the first inductance, the second diode, the first switching device, the described first end of the first inductance is connected with the positive pole of DC power supply, second end of the first inductance is connected with the first end of the first switching device with the anode of the second diode, the negative pole of the second termination DC power supply of the first switching device, the negative electrode of the second diode connects the second end of described by-pass unit; Inverter circuit comprises the 4th switching device, the 5th switching device, the 6th switching device and the 7th switching device, 4th switching device and the 5th switching device are connected in series formation first branch road, 6th switching device and the 7th switching device are connected in series formation second branch road, first branch road and the second branch road are connected in parallel on the output of reduction voltage circuit respectively, the tie point of the 4th switching device and the 5th switching device draws the first end connecing AC load, and the tie point of the 6th switching device and the 7th switching device draws the second end connecing AC load; First energy storage filter unit comprises the first electric capacity, the negative electrode of the first termination second diode of the first electric capacity, the negative pole of the second termination DC power supply of the first electric capacity; Above-mentioned reduction voltage circuit comprises a buck circuit, one buck circuit comprises second switch device, the 3rd diode, the second inductance, the first end of second switch device is connected with the first end of the first electric capacity, second end of second switch device is connected with the first end of the second inductance with the negative electrode of the 3rd diode, the anode of the 3rd diode connects the second end of the first electric capacity, and the second end of the second inductance is connected with inverter circuit; The main points of the operation method of described voltage changer are, when described direct voltage is less than line voltage peak value, size between the absolute value judging direct voltage and line voltage instantaneous value, if direct voltage is not less than the absolute value of line voltage instantaneous value, first switching device turns off, and second switch device is by high-frequency signal trigger action; If direct voltage is less than the absolute value of line voltage instantaneous value, the first switching device by high-frequency signal trigger action, second switch break-over of device; When described direct voltage is not less than line voltage peak value, the first switching device turns off, and second switch device is by high-frequency signal trigger action.
Further, at the positive half cycle of alternating voltage, the 4th switching device and the 7th switch device conductive, the 5th switching device and the 6th switching device turn off; At the negative half period of alternating voltage, the 4th switching device and the 7th switching device turn off, the 5th switching device and the 6th switch device conductive.
Further, above-mentioned voltage changer also comprises the second energy storage filter unit be connected between reduction voltage circuit and inverter circuit, and the high fdrequency component in the absolute value voltage of the sine wave AC voltage exported for reduction voltage circuit described in filtering also generates the second intermediate voltage and exports to inverter circuit.
According to the operation method of above-mentioned voltage changer, when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work, and therefore conversion efficiency is improved.
Further, in each work period of alternating voltage, only have a switching device to be in high-frequency work state, system switching loss reduces simultaneously; In addition, the 4th switching device is in power frequency operating state to the 7th switching device, therefore can select the switching tube at a slow speed that conduction voltage drop is lower, thus improves the conversion efficiency of voltage changer further, reduces costs simultaneously.
The embodiment of the present invention additionally provides a kind of operation method of voltage changer, the converting direct-current voltage into alternating-current voltage that described voltage changer is used for DC power supply exports is supplied to AC load, comprises booster circuit, the first energy storage filter unit, reduction voltage circuit, inverter circuit and by-pass unit, the input of described booster circuit is connected in the two ends of DC power supply in parallel, between the output that described first energy storage filter unit, reduction voltage circuit and inverter circuit order is connected in described booster circuit in parallel and AC load, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit, the direct voltage that described booster circuit is used for DC power supply exports is converted to higher direct voltage and exports, described first energy storage filter unit is used for the high fdrequency component in the higher direct voltage that described in filtering, booster circuit exports and generates the first intermediate voltage exporting, described first intermediate voltage is converted to the absolute value voltage of sine wave AC voltage by described reduction voltage circuit, the absolute value voltage of the sine wave AC voltage that described reduction voltage circuit exports by inverter circuit carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load, described by-pass unit is used for during described direct voltage is not less than the absolute value of line voltage instantaneous value, by described booster circuit bypass, booster circuit comprises the first inductance, the second diode, the first switching device, the described first end of the first inductance is connected with the positive pole of DC power supply, second end of the first inductance is connected with the first end of the first switching device with the anode of the second diode, the negative pole of the second termination DC power supply of the first switching device, the negative electrode of the second diode connects the second end of described by-pass unit, inverter circuit comprises the 4th switching device, the 5th switching device, the 6th switching device and the 7th switching device, 4th switching device and the 5th switching device are connected in series formation first branch road, 6th switching device and the 7th switching device are connected in series formation second branch road, first branch road and the second branch road are connected in parallel on the output of reduction voltage circuit respectively, the tie point of the 4th switching device and the 5th switching device draws the first end connecing AC load, and the tie point of the 6th switching device and the 7th switching device draws the second end connecing AC load, first energy storage filter unit comprises the first electric capacity, the negative electrode of the first termination second diode of the first electric capacity, the negative pole of the second termination DC power supply of the first electric capacity, described reduction voltage circuit comprises a buck circuit and the 2nd buck circuit, one buck circuit comprises second switch device, 3rd diode, second inductance, 2nd buck circuit comprises the 3rd switching device, 3rd inductance, the first end of second switch device is connected with the first end of the first electric capacity, second end of second switch device is connected with the first end of the second inductance with the negative electrode of the 3rd diode, second end of the second inductance is connected with the first end of the 6th switching device with the first end of the 4th switching device, the first end of the 3rd switching device is connected with the second end of the first electric capacity, second end of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 3rd diode, second end of the 3rd inductance is connected with the second end of the 7th switching device with the second end of the 5th switching device, preferably, the second switch device in above-mentioned voltage changer and the 3rd switching device, the second inductance and the 3rd inductance select the electronic devices and components into same model respectively.The main points of the operation method of described voltage changer are, when described direct voltage is less than line voltage peak value, size between the absolute value judging direct voltage and line voltage instantaneous value, if direct voltage is not less than the absolute value of line voltage instantaneous value, first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action; If direct voltage is less than the absolute value of line voltage instantaneous value, the first switching device by high-frequency signal trigger action, second switch device and the 3rd switch device conductive; When described direct voltage is not less than line voltage peak value, the first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action.
Further, at the positive half cycle of alternating voltage, the 4th switching device and the 7th switch device conductive, the 5th switching device and the 6th switching device turn off; At the negative half period of alternating voltage, the 4th switching device and the 7th switching device turn off, the 5th switching device and the 6th switch device conductive.
Further, above-mentioned voltage changer also comprises the second energy storage filter unit be connected between reduction voltage circuit and inverter circuit, and the high fdrequency component in the absolute value voltage of the sine wave AC voltage exported for reduction voltage circuit described in filtering also generates the second intermediate voltage and exports to described inverter circuit.
According to the operation method of above-mentioned voltage changer, during the direct voltage of DC power supply output is not less than the absolute value of line voltage instantaneous value, booster circuit does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work, and therefore conversion efficiency is improved.
Further, reduction voltage circuit adopts symmetrical circuit structure, inhibits by the DC power supply leakage current that flows through of parasitic capacitance over the ground, improves the functional reliability of voltage changer, improve the performance of voltage changer electromagnetism interference.
In addition, the symmetric part of reduction voltage circuit selects electric property and the identical electronic devices and components of parameter, thus further suppress by DC power supply over the ground parasitic capacitance flow through leakage current, the functional reliability that improve voltage changer, improve the performance of voltage changer electromagnetism interference.
In addition, in each work period of alternating voltage, second switch device is identical with the triggering signal of the 3rd switching device, the voltage of half can be born respectively, therefore second switch device and the 3rd switching device can select the switching tube that tube voltage drop is lower, improve conversion efficiency, reduce cost; Meanwhile, the 4th switching device is in power frequency operating state to the 7th switching device, therefore can select the switching tube at a slow speed that conduction voltage drop is lower, thus further increase conversion efficiency, reduce cost.
The embodiment of the present invention additionally provides a kind of operation method of voltage changer, the converting direct-current voltage into alternating-current voltage that described voltage changer is used for DC power supply exports is supplied to AC load, comprises booster circuit, the first energy storage filter unit, reduction voltage circuit, inverter circuit and by-pass unit, the input of described booster circuit is connected in the two ends of DC power supply in parallel, between the output that described first energy storage filter unit, reduction voltage circuit and inverter circuit order is connected in described booster circuit in parallel and AC load, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit, the direct voltage that described booster circuit is used for DC power supply exports is converted to higher direct voltage and exports, described first energy storage filter unit is used for the high fdrequency component in the higher direct voltage that described in filtering, booster circuit exports and generates the first intermediate voltage exporting, described first intermediate voltage is converted to the absolute value voltage of sine wave AC voltage by described reduction voltage circuit, the absolute value voltage of the sine wave AC voltage that described reduction voltage circuit exports by inverter circuit carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load, described by-pass unit is used for during described direct voltage is not less than the absolute value of line voltage instantaneous value, by described booster circuit bypass, booster circuit comprises the first inductance, the second diode, the first switching device, the described first end of the first inductance is connected with the positive pole of DC power supply, second end of the first inductance is connected with the first end of the first switching device with the anode of the second diode, the negative pole of the second termination DC power supply of the first switching device, the negative electrode of the second diode connects the second end of described by-pass unit, inverter circuit comprises the 4th switching device, the 5th switching device, the 6th switching device and the 7th switching device, 4th switching device and the 5th switching device are connected in series formation first branch road, 6th switching device and the 7th switching device are connected in series formation second branch road, first branch road and the second branch road are connected in parallel on the output of reduction voltage circuit respectively, the tie point of the 4th switching device and the 5th switching device draws the first end connecing AC load, and the tie point of the 6th switching device and the 7th switching device draws the second end connecing AC load, first energy storage filter unit comprises the first electric capacity and the second electric capacity that are mutually connected in series, the negative electrode of the first termination second diode of the first electric capacity, second end of the first electric capacity be connected with the first end of the second electric capacity and tie point for generation of the midpoint potential of described first intermediate voltage, the negative pole of the second termination DC power supply of the second electric capacity, described reduction voltage circuit comprises the buck circuit and the 2nd buck circuit that are mutually connected in series, one buck circuit comprises second switch device, 3rd diode, second inductance, 2nd buck circuit comprises the 3rd switching device, 4th diode, 3rd inductance, the first end of second switch device is connected with the first end of the first electric capacity, second end of second switch device is connected with the first end of the second inductance with the negative electrode of the 3rd diode, the anode of the 3rd diode is connected with the negative electrode of the 4th diode and tie point connects the midpoint potential of described first intermediate voltage, second end of the first termination second electric capacity of the 3rd switching device, second termination of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 4th diode, second end of the second inductance is connected with the first end of the 6th switching device with the first end of the 4th switching device, second end of the 3rd inductance is connected with the second end of the 7th switching device with the second end of the 5th switching device, preferably, the first electric capacity in above-mentioned voltage changer and the second electric capacity, second switch device and the 3rd switching device, the 3rd diode and the 4th diode, the second inductance and the 3rd inductance select the electronic devices and components into same model respectively.The main points of the operation method of described voltage changer are, when described direct voltage is less than line voltage peak value, size between the absolute value judging direct voltage and line voltage instantaneous value, if direct voltage is not less than the absolute value of line voltage instantaneous value, first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action; If direct voltage is less than the absolute value of line voltage instantaneous value, the first switching device by high-frequency signal trigger action, second switch device and the 3rd switch device conductive; When described direct voltage is not less than line voltage peak value, the first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action.
Further, at the positive half cycle of alternating voltage, the 4th switching device and the 7th switch device conductive, the 5th switching device and the 6th switching device turn off; At the negative half period of alternating voltage, the 4th switching device and the 7th switching device turn off, the 5th switching device and the 6th switch device conductive.
Further, above-mentioned voltage changer also comprises the second energy storage filter unit be connected between reduction voltage circuit and inverter circuit, and the high fdrequency component in the absolute value voltage of the sine wave AC voltage exported for reduction voltage circuit described in filtering also generates the second intermediate voltage and exports to described inverter circuit.
According to the operation method of above-mentioned voltage changer, during the direct voltage of DC power supply output is not less than the absolute value of line voltage instantaneous value, booster circuit does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply exports is not less than the absolute value of line voltage instantaneous value, booster circuit does not work, and therefore conversion efficiency is improved.
Further, the first energy storage filter unit and reduction voltage circuit adopt symmetrical circuit structure, inhibit by the DC power supply leakage current that flows through of parasitic capacitance over the ground, improve the functional reliability of voltage changer, improve the performance of voltage changer electromagnetism interference.
In addition, first energy storage filter unit and reduction voltage circuit symmetric part separately select electric property and the identical electronic devices and components of parameter, thus further suppress by DC power supply over the ground parasitic capacitance flow through leakage current, the functional reliability that improve voltage changer, improve the performance of voltage changer electromagnetism interference.
In addition, in each work period of alternating voltage, second switch device is identical with the triggering signal of the 3rd switching device, and the 3rd diode and the 4th Diode series are connected between the positive direct-current bus of voltage changer and negative DC bus, therefore second switch device and the 3rd switching device can select the switching tube that tube voltage drop is lower, 3rd diode and the 4th diode can select the diode that tube voltage drop is lower, improve conversion efficiency, reduce cost; Meanwhile, the 4th switching device is in power frequency operating state to the 7th switching device, therefore can select the switching tube at a slow speed that conduction voltage drop is lower, thus further increase conversion efficiency, reduce cost.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment below, apparently, the accompanying drawing that the following describes is only some embodiments recorded in the present invention, for those of ordinary skill in the art, other accompanying drawing can also be obtained according to these accompanying drawings.
Fig. 1 is the theory diagram of the embodiment of the present invention;
Fig. 2 is the circuit diagram of the embodiment of the present invention one;
Fig. 3 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating current positive pressure half cycle, second switch device are opened;
Fig. 4 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe not less than | U ac (t)|, alternating current positive pressure half cycle, second switch device turn off time current direction schematic diagram;
Fig. 5 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating voltage negative half period, second switch device are opened;
Fig. 6 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe not less than | U ac (t)|, alternating voltage negative half period, second switch device turn off time current direction schematic diagram;
Fig. 7 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe less than | U ac (t)|, current direction schematic diagram when alternating current positive pressure half cycle, the first switching device are opened;
Fig. 8 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe less than | U ac (t)|, alternating current positive pressure half cycle, first switching device turn off time current direction schematic diagram;
Fig. 9 is for circuit shown in Fig. 2 is at periods of low pressure, U dcbe less than | U ac (t)|, alternating voltage negative half period, first switching device turn off time current direction schematic diagram;
Figure 10 is for circuit shown in Fig. 2 is in the drive signal waveform of each switching device of periods of low pressure and first, second intermediate voltage oscillogram;
Figure 11 is for circuit shown in Fig. 2 is in the drive signal waveform of each switching device of high pressure phase and first, second intermediate voltage oscillogram;
Figure 12 is the circuit diagram of the embodiment of the present invention two;
Figure 13 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating current positive pressure half cycle, second switch device and the 3rd switching device are opened;
Figure 14 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating current positive pressure half cycle, second switch device and the 3rd switching device turn off;
Figure 15 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating voltage negative half period, second switch device and the 3rd switching device are opened;
Figure 16 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe not less than | U ac (t)|, current direction schematic diagram when alternating voltage negative half period, second switch device and the 3rd switching device turn off;
Figure 17 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe less than | U ac (t)|, current direction schematic diagram when alternating current positive pressure half cycle, the first switching device are opened;
Figure 18 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe less than | U ac (t)|, alternating current positive pressure half cycle, first switching device turn off time current direction schematic diagram;
Figure 19 is for circuit shown in Figure 12 is at periods of low pressure, U dcbe less than | U ac (t)|, alternating voltage negative half period, first switching device turn off time current direction schematic diagram;
Figure 20 is for circuit shown in Figure 12 is in the drive signal waveform of each switching device of periods of low pressure and first, second intermediate voltage oscillogram;
Figure 21 is for circuit shown in Figure 12 is in the drive signal waveform of each switching device of high pressure phase and first, second intermediate voltage oscillogram;
Figure 22 is the circuit diagram of the embodiment of the present invention three.
Embodiment
In order to the scheme making those skilled in the art person understand the embodiment of the present invention better, below in conjunction with drawings and embodiments, the embodiment of the present invention is described in further detail.
The object of the embodiment of the present invention is to provide relative to prior art, the voltage changer that conversion efficiency is high, cost is low and operation method thereof.
With reference to Fig. 1, the theory diagram of voltage changer disclosed in the embodiment of the present invention.Described voltage changer is used for the converting direct-current voltage into alternating-current voltage that DC power supply 1 exports to be supplied to AC load 8, this voltage changer comprises booster circuit 2, the first energy storage filter unit 3, reduction voltage circuit 4, the inverter circuit 6 that are linked in sequence between DC power supply 1 and AC load 8, and the by-pass unit 7 to be connected with booster circuit 2, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit;
Booster circuit 2 is converted to higher direct voltage for direct voltage DC power supply 1 exported and exports;
High fdrequency component in the higher direct voltage that first energy storage filter unit 3 exports for booster circuit described in filtering 2 also generates the first intermediate voltage U d1export;
Described reduction voltage circuit 4 is by described first intermediate voltage U d1be converted to the absolute value voltage of sine wave AC voltage;
The absolute value voltage of the sine wave AC voltage that described reduction voltage circuit 4 exports by inverter circuit 6 carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load 8;
Corresponding to complete work period, above-mentioned sinusoidal voltage is by a positive half wave of sine wave and negative half wave component; The absolute value voltage of sine wave AC voltage is made up of two positive half waves.
By-pass unit 7 for be not less than line voltage instantaneous value at direct voltage absolute value during, by booster circuit 2 bypass.
Further, by-pass unit 7 is the first diode D1, and the anode of the first diode D1 connects the positive pole of DC power supply 1, and the negative electrode of the first diode D1 connects the negative electrode of the second diode D2.Utilize the blocking characteristics of diode self to realize the bypass functionality of by-pass unit, circuit is simple.
Further, this voltage changer also comprises the second energy storage filter unit 5, be connected between reduction voltage circuit 4 and inverter circuit 6, for reduction voltage circuit described in filtering 4 export sine wave AC voltage absolute value voltage in high fdrequency component and generate the second intermediate voltage U d2export to inverter circuit 6.
It should be noted that, in the embodiment of the present invention, DC power supply 1 can be solar panel or by multiple solar panel DC source such as photovoltaic string, wind turbine, storage battery or fuel cell with rectification circuit formed connected in series or in parallel, DC power supply 1 has parasitic capacitance over the ground;
The interchange dissipative load of AC load 8 both can be operating frequency be 50Hz or 60Hz also can be rated frequency is the AC network of 50Hz or 60Hz.That is, the voltage changer in the embodiment of the present invention both can work in the pattern of being incorporated into the power networks, and also can work in independent operation mode.When work in be incorporated into the power networks pattern time, can be connected in the load (not drawing in the drawings) of user between voltage changer and AC network, voltage changer control voltage converter and AC network provide the collaborative running of alternating current to load.
According to above-mentioned voltage changer, when the direct voltage that DC power supply 1 exports is not less than the absolute value of line voltage instantaneous value, booster circuit 2 does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit 2 just works, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply 1 exports is not less than the absolute value of line voltage instantaneous value, booster circuit 2 does not work, and therefore conversion efficiency is improved.
As shown in Figure 2, be the circuit diagram of voltage changer of the embodiment of the present invention one.
In this embodiment, booster circuit 2 comprises the first inductance L 1, second diode D2, the first switching device S1, the first end of the first inductance L 1 is connected with the positive pole of DC power supply 1, second end of the first inductance L 1 is connected with the first end of the first switching device S1 with the anode of the second diode D2, the negative pole of the second termination DC power supply 1 of the first switching device S1;
The first end of by-pass unit 7 is connected with the positive pole of DC power supply 1, the negative electrode of the second termination second diode D2 of by-pass unit 7;
Inverter circuit 6 comprises the 4th switching device S4, 5th switching device S5, 6th switching device S6 and the 7th switching device S7, 4th switching device S4 and the 5th switching device S5 is connected in series formation first branch road, 6th switching device S6 and the 7th switching device S7 is connected in series formation second branch road, first branch road and the second branch road are connected in parallel on the two ends of reduction voltage circuit 4 respectively, the tie point of the 4th switching device S4 and the 5th switching device S5 draws the first end connecing AC load 8, the tie point of the 6th switching device S6 and the 7th switching device S7 draws the second end connecing AC load 8.
Further, the first energy storage filter unit 3 is the first electric capacity C1, the negative electrode of the first termination second diode D2 of the first electric capacity C1, the negative pole of the second termination DC power supply 1 of the first electric capacity C1.The direct voltage of the first electric capacity C1 booster circuit 2 output carries out filtering and exports the first intermediate voltage U d1;
First electric capacity C1 can choose the less electric capacity of capacitance, is generally no more than tens of uF, such as, selects thin-film capacitor, and its life-span is long, adds reliability and the life-span of inverter.
Reduction voltage circuit 4 is a buck circuit, one buck circuit comprises second switch device S2, the 3rd diode D3, the second inductance L 2, the first end of second switch device S2 is connected with the first end of the first electric capacity C1, second end of second switch device S2 is connected with the first end of the second inductance L 2 with the negative electrode of the 3rd diode D3, the anode of the 3rd diode D3 connects second end of the first electric capacity C1, and the second end of the second inductance L 2 is connected with the first end of the 6th switching device with the first end of the 4th switching device.
Further, by-pass unit 7 is the first diode D1, and the anode of the first diode D1 connects the positive pole of DC power supply 1, and the negative electrode of the first diode D1 connects the negative electrode of the second diode D2.Utilize the blocking characteristics of diode self to realize the bypass functionality of by-pass unit, circuit is simple.
Further, this voltage changer also comprises the second energy storage filter unit 5, is connected between reduction voltage circuit 4 and inverter circuit 6, in the present embodiment, second energy storage filter unit 5 is the 3rd electric capacity C3, for the high fdrequency component in the input terminal voltage of filtering inverter circuit 6, exports the second intermediate voltage U d2;
The first end of the 3rd electric capacity C3 is connected with the first end of the 6th switching device with the first end of the 4th switching device, and second end of the 3rd electric capacity C3 is connected with the second end of the 7th switching device with the second end of the 5th switching device.
3rd electric capacity C3 can choose the less electric capacity of capacitance, is generally no more than tens of uF, such as thin-film capacitor, and its life-span is long, adds reliability and the life-span of inverter.
Meanwhile, due to the existence of the 3rd electric capacity C3, the first electric capacity C1 is not when booster circuit 2 is bypassed, and filtering common with the first inductance L 1 in booster circuit 2, therefore the capacitance of the first electric capacity C1 can be chosen less.
It should be noted that, in the embodiment of the present invention, by-pass unit 7 is selected diode to realize, in reality, other electronic devices and components possessing block function also can be selected to realize by the function of booster circuit 2 bypass during the direct voltage of DC power supply 1 is not less than the absolute value of line voltage instantaneous value, such as relay, contactor or switching tube etc.
Also it should be noted that, above-mentioned 4th switching device S4 selects the switching device of same model to the 7th switching device S7, preferred IGBT; When selecting IGBT, the first end of switching device refers to the collector electrode of IGBT, and the second end of switching device refers to the emitter of IGBT;
First switching device S1 and the preferred MOSFET of second switch device S2; When selecting MOSFET, the first end of switching device refers to the drain electrode of MOSFET, and the second end of switching device refers to the source electrode of MOSFET.
According to above-mentioned voltage changer, when the direct voltage that DC power supply 1 exports is not less than the absolute value of line voltage instantaneous value, booster circuit 2 does not work; Be less than the absolute value of line voltage instantaneous value at direct voltage during, booster circuit 2 just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And when the direct voltage that DC power supply 1 exports is not less than the absolute value of line voltage instantaneous value, booster circuit 2 does not work, and therefore conversion efficiency is improved.
The operation method of the voltage changer (physical circuit as shown in Figure 2) described in the embodiment of the present invention one is described in detail below in conjunction with Fig. 3 to Figure 11.
Fig. 3 to Fig. 9 gives the current direction schematic diagram of voltage changer within a work period of the embodiment of the present invention one, and in the embodiment of the present invention, the positive half cycle of alternating voltage that exported by voltage changer of a work period of indication and negative half period form.
Figure 10, Figure 11 sets forth the drive signal waveform of the embodiment of the present invention one each switching device in periods of low pressure, high pressure phase voltage changer.
For convenience, U is defined dcfor the direct voltage that DC power supply 1 exports, | U ac (t)| be the absolute value of line voltage instantaneous value, U ac (max)for line voltage peak value, definition U dcbe not less than U ac (max)during be high pressure phase, definition U dcbe less than U ac (max)during be periods of low pressure.
First set forth the operation method of voltage changer in periods of low pressure of the embodiment of the present invention one below in conjunction with Fig. 3 to Figure 10, for convenience, the positive half cycle of point alternating voltage and negative half period launch to discuss.
1, the positive half cycle of alternating voltage
The 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 conducting, the 5th switching device S5 and the 6th switching device S6 turns off.
(1) U is worked as dcbe not less than | U ac (t)| time
Booster circuit 2 does not work, and the first switching device S1 turns off; Second switch device S2 in reduction voltage circuit 4 is by high-frequency signal trigger action.
A, when the S2 conducting of second switch device, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 3, second switch device S2, second inductance L 2 and the inverter circuit 6 of the electric current that DC power supply 1 exports directly in the first diode D1, reduction voltage circuit 4 of by-pass unit is to AC load 8, and current path is DC power supply 1 positive pole-D1-S2-L2-S4-AC load 8-S7-DC power supply 1 negative pole.
B, when second switch device S2 turns off, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 4, the electric current that DC power supply 1 exports is by the 3rd diode D3 afterflow in reduction voltage circuit 4, current path is L2-S4-AC load 8-S7-D3-L2, can find out, interchange continuous current circuit and DC side disconnect completely.
(2) U is worked as dcbe less than | U ac (t)| time
During this period, the second switch device S2 in reduction voltage circuit 4 is open-minded; Booster circuit 2 works, and the first switching device S1 is triggered by high-frequency signal.
A, when the first switching device S1 conducting, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 7, DC power supply 1 export direct voltage U dcboost through booster circuit 2.Current path is: DC power supply 1 positive pole-L1-S1-DC power supply 1 negative pole.
B, when first switching device S1 turn off time, as shown in Figure 8, current path is DC power supply 1 positive pole-L1-D2-S2-L2-S4-AC load 8-S7-DC power supply 1 negative pole to the current direction of the voltage changer of the embodiment of the present invention one.
2, the negative half period of alternating voltage
The 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 turns off, the 5th switching device S5 and the 6th switching device S6 conducting.
(1) U is worked as dcbe not less than | U ac (t)| time
Booster circuit 2 does not work, and the first switching device S1 turns off; Second switch device S2 in reduction voltage circuit 4 is triggered by high-frequency signal.
A, when the S2 conducting of second switch device, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 5, second switch device S2, second inductance L 2 and the inverter circuit 6 of electric current directly in the first diode D1, reduction voltage circuit 4 of by-pass unit is to AC load 8, and current path is DC power supply 1 positive pole-D1-S2-L2-S6-AC load 8-S5-DC power supply 1 negative pole.
B, when second switch device S2 turns off, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 6, electric current is by the 3rd diode D3 in reduction voltage circuit 4 and the second inductance L 2 afterflow, current path is L2-S6-AC load 8-S5-I3-L2, can find out, interchange continuous current circuit and DC side disconnect completely.
(2) U is worked as dcbe less than | U ac (t)| time
During this period, the second switch device S2 in reduction voltage circuit 4 is open-minded; Booster circuit 2 works, and the first switching device S1 is triggered by high-frequency signal.
A, when the first switching device S1 conducting, the current direction of the voltage changer of the embodiment of the present invention one as shown in Figure 7, DC power supply 1 export direct voltage U dcboost through booster circuit 2.Current path is: DC power supply 1 positive pole-L1-S1-DC power supply 1 negative pole.
B, when first switching device S1 turn off time, as shown in Figure 9, current path is DC power supply 1 positive pole-L1-D2-S2-L2-S6-AC load 8-S5-DC power supply 1 negative pole to the current direction of the voltage changer of the embodiment of the present invention one.
It should be noted that, the high-frequency pulse signal described in the embodiment of the present invention is pulse signal within the scope of KHz or pulse width modulating signal, and the frequency of power frequency pulse signal is 50Hz or 60Hz.
Above the voltage changer of the embodiment of the present invention one shown in Fig. 2 is described in the course of work of periods of low pressure.
As can be seen from Figure 10, the first intermediate voltage U d1be the waveform of part for convex, that wherein convex waveform portion is corresponding is U dcbe less than | U ac (t)| period, during namely booster circuit 2 works; Second intermediate voltage U d2be through the absolute value voltage of filtered sine wave AC voltage, the sine wave AC voltage that the absolute value voltage of this filtered sine wave AC voltage generates standard after the commutation of inverter circuit 6 power frequency is supplied to AC load 8.
Set forth the operation method of the voltage changer of the embodiment of the present invention one at high pressure phase below in conjunction with Figure 11, at high pressure phase, booster circuit 2 does not work, and the first switching device S1 turns off always; Second switch device S2 in reduction voltage circuit 4 is triggered by high-frequency signal.Equally, at the positive half cycle of alternating voltage, the 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 conducting, the 5th switching device S5 and the 6th switching device S6 turns off; At the negative half period of alternating voltage, the 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 turns off, the 5th switching device S5 and the 6th switching device S6 conducting.Because definition high pressure phase is direct voltage U dcbe not less than line voltage peak value U ac (max)situation, therefore there is not U dcbe less than | U ac (t)| situation, the voltage changer of the embodiment of the present invention one high pressure phase current direction figure as shown in Figures 3 to 6, the detailed course of work and above periods of low pressure U dcbe not less than | U ac (t)| the course of work identical.
As can be seen from Figure 11, because booster circuit 2 does not work at high pressure phase, the tube voltage drop of the first diode D1 is very little, negligible, therefore the first intermediate voltage U d1size equal the direct voltage U of DC power supply 1 dc; Second intermediate voltage U d2be the absolute value voltage of filtered sine wave AC voltage, the sine wave AC voltage that the absolute value voltage of this filtered sine wave AC voltage generates standard after the commutation of inverter circuit 6 power frequency is supplied to AC load 8.
According to the operation method of above-mentioned voltage changer, at the direct voltage U that DC power supply 1 exports dcbe not less than the absolute value of line voltage instantaneous value | U ac (t)| during, booster circuit 2 does not work; At direct voltage U dcbe less than the absolute value of line voltage instantaneous value | U ac (t)| during, booster circuit 2 just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And at the direct voltage U that DC power supply 1 exports dcbe not less than the absolute value of line voltage instantaneous value | U ac (t)| when, booster circuit 2 does not work, and therefore conversion efficiency is also improved.
And, in each work period of alternating voltage, only have a switching device (S1 or S2) to be in high-frequency work state simultaneously, system switching loss reduces, meanwhile, the 4th switching device S4 is in power frequency operating state to the 7th switching device S7, therefore can select the switching tube at a slow speed that conduction voltage drop is lower, thus improve the conversion efficiency of voltage changer further, reduce costs simultaneously.
The circuit diagram of the embodiment of the present invention two as shown in figure 12.
As can be seen from Figure 12, relative to the embodiment of the present invention one (physical circuit is shown in Fig. 2), the difference of the voltage changer of the embodiment of the present invention two is, first energy storage filter unit 3 also comprises the second electric capacity C2 be connected in series with the first electric capacity C1, first electric capacity C1 connects the negative pole of DC power supply 1 through the second electric capacity C2, second end of the first electric capacity C1 be connected with the first end of the second electric capacity C2 and tie point for generation of the first intermediate voltage U d1midpoint potential, the negative pole of the second termination DC power supply 1 of the second electric capacity C2; Described reduction voltage circuit 4 also comprises the 2nd buck circuit, 2nd buck circuit comprises the 3rd switching device S3, the 4th diode D4, the 3rd inductance L 3, the first end of second switch device S2 is connected with the first end of the first electric capacity C1, second end of second switch device S2 is connected with the first end of the second inductance L 2 with the negative electrode of the 3rd diode D3, and the anode of the 3rd diode D3 is connected with the negative electrode of the 4th diode D4 and tie point meets described first intermediate voltage U d1midpoint potential, second end of the first termination second electric capacity C2 of the 3rd switching device S3, second termination of the 3rd switching device S3 is connected with the first end of the 3rd inductance L 3 with the anode of the 4th diode D4, second end of the second inductance L 2 is connected with the first end of the 6th switching device with the first end of the 4th switching device, and the second end of the 3rd inductance L 3 is connected with the second end of the 7th switching device with the second end of the 5th switching device.
Further, the first electric capacity C1 and the second electric capacity C2, second switch device S2 and the 3rd switching device S3, the 3rd diode D3 and the 4th diode D4, the second inductance L 2 and the 3rd inductance L 3 are respectively the electronic devices and components of same model.
With the embodiment of the present invention one in like manner, due to the existence of the 3rd electric capacity C3, the first electric capacity C1 and the second electric capacity C2 can choose the less electric capacity of capacitance, is generally no more than tens of uF, such as thin-film capacitor.
It should be noted that, because the first electric capacity C1 and the second electric capacity C2 participates in filtering jointly in practical application, the value in the comparable embodiment of the present invention of the first electric capacity C1 value one is little.
Second switch device S2 and the preferred MOSFET of the 3rd switching device S3; When selecting MOSFET, the first end of switching device refers to the drain electrode of MOSFET, and the second end of switching device refers to the source electrode of MOSFET.
Other parts of the embodiment of the present invention two voltage converter circuit and requirement, with embodiment one, repeat no more herein.
The operation method of voltage changer shown in Figure 12 is described in detail below in conjunction with Figure 13 to Figure 21.
For convenience of description, U is defined aOfor the voltage of A point and O point in figure, U bOfor the voltage of B point and O point in figure, U cMfor common-mode voltage, i cMfor common mode leakage current, C cMfor the capacitance of DC power supply 1 parasitic capacitance over the ground, i.e. common mode capacitance capacitance.
Figure 13 to Figure 19 gives its current direction schematic diagram under various operating state, and Figure 20, Figure 21 sets forth the drive signal waveform of voltage changer at periods of low pressure, each switching device of high pressure phase of the embodiment of the present invention two.
First set forth the operation method of voltage changer in periods of low pressure of the embodiment of the present invention two below in conjunction with Figure 13 to Figure 20, for convenience, the positive half cycle of point alternating voltage and negative half period launch to discuss.
1, the positive half cycle of alternating voltage
The 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 conducting, the 5th switching device S5 and the 6th switching device S6 turns off.
(1) U is worked as dcbe not less than | U ac (t)| time
Booster circuit 2 does not work, and the first switching device S1 turns off; Second switch device S2 in reduction voltage circuit 4 and the 3rd switching device S3 is synchronously triggered by high-frequency signal.
A, as second switch device S2 and the 3rd switching device S3 conducting, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 13, the electric current that DC power supply 1 exports directly arrives AC load 8 through the first diode D1 of by-pass unit, reduction voltage circuit 4 and inverter circuit 6, and current path is DC power supply 1 positive pole-D1-S2-L2-S4-AC load 8-S7-L3-S3-DC power supply 1 negative pole.
Now, U aO=U dc, U bO=0, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U dc/2 (1)
B, when second switch device S2 and the 3rd switching device S3 turn off, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 14, electric current is by the 3rd diode D3, the 4th diode D4 in reduction voltage circuit 4, the second inductance L 2, the 3rd inductance L 3 afterflow, current path is L2-S4-AC load 8-S7-L 3-D4-D3-L2, can find out, interchange continuous current circuit and DC side disconnect completely.
Now, U aO=U bO=U dc/ 2, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U dc/2 (2)
(2) U is worked as dcbe less than | U ac (t)| time
During this period, the second switch device S2 in reduction voltage circuit 4 and the 3rd switching device S3 is open-minded; Booster circuit 2 works, and the first switching device S1 is triggered by high-frequency signal.
A, when the first switching device S1 conducting, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 17, DC power supply 1 export direct voltage U dcboost through booster circuit 2.Current path is: DC power supply 1 positive pole-L1-S1-DC power supply 1 negative pole.
Now, U aO=U d1, U bO=0, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U d1/2 (3)
B, when first switching device S1 turn off time, as shown in figure 18, current path is DC power supply 1 positive pole-L1-D2-S2-L2-S4-AC load 8-S7-L3-S3-DC power supply 1 negative pole to the current direction of the voltage changer of the embodiment of the present invention one.
Now, U aO=U bO=U d1/ 2, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U d1/2 (4)
2, the negative half period of alternating voltage
The 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 turns off, the 5th switching device S5 and the 6th switching device S6 conducting.
(1) U is worked as dcbe not less than | U ac (t)| time
Booster circuit 2 does not work, and the first switching device S1 turns off; Second switch device S2 in reduction voltage circuit 4 and the 3rd switching device S3 is triggered by high-frequency signal.
A, as second switch device S2 and the 3rd switching device S3 conducting, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 15, electric current directly arrives AC load 8 through the first diode D1 of by-pass unit, reduction voltage circuit 4 and inverter circuit 6, and current path is DC power supply 1 positive pole-D1-S2-L2-S6-AC load 8-S5-L3-S3-DC power supply 1 negative pole.
Now, U aO=U dc, U bO=0, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U dc/2 (5)
B, when second switch device S2 and the 3rd switching device S3 turn off, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 16, electric current is by the 3rd diode D3, the 4th diode D4 in reduction voltage circuit 4, the second inductance L 2, the 3rd inductance L 3 afterflow, current path is L2-S6-AC load 8-S5-L3-D4-D3-L2, can find out, interchange continuous current circuit and DC side disconnect completely.
Now, U aO=U bO=U dc/ 2, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U dc/2 (6)
(2) U is worked as dcbe less than | U ac (t)| time
During this period, the second switch device S2 in reduction voltage circuit 4 and the 3rd switching device S3 is open-minded; Booster circuit 2 works, and the first switching device S1 is triggered by high-frequency signal.
A, when the first switching device S1 conducting, the current direction of the voltage changer of the embodiment of the present invention two as shown in figure 17, DC power supply 1 export direct voltage U dcboost through booster circuit 2.Current path is: DC power supply 1 positive pole-L1-S1-DC power supply 1 negative pole.
Now, U aO=U d1, U bO=0, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U d1/2 (7)
B, when first switching device S1 turn off time, as shown in figure 19, current path is DC power supply 1 positive pole-L1-D2-S2-L2-S6-AC load 8-S5-L 3-S 3-DC power supply 1 negative pole to the current direction of the voltage changer of the embodiment of the present invention two.
Now, U aO=U bO=U d1/ 2, the common-mode voltage of inverter is:
U CM(U AO+U BO)/2＝U d1/2 (8)
As can be seen from the above-mentioned analysis to voltage changer operation method, due to U d1with U dcapproximately equal, therefore, common-mode voltage U cMalmost invariable in the whole cycle of alternating voltage, by common-mode voltage U cMmode ship current i together cMbetween relation (i cM=C cMdV cM/ dt) known, common mode leakage current i cMbe approximately zero.
Above the voltage changer of the embodiment of the present invention two shown in Figure 12 is described at the operation method of periods of low pressure.
As can be seen from Figure 20, the first intermediate voltage U d1be the waveform of part for convex, that wherein male member is corresponding is U dcbe less than | U ac (t)| period, namely during booster circuit work; Second intermediate voltage U d2be the absolute value voltage of filtered sine wave AC voltage, the sine wave AC voltage that the absolute value voltage of this filtered sine wave AC voltage generates standard after the commutation of inverter circuit 6 power frequency is supplied to AC load 8.
Set forth the operation principle of the voltage changer of the embodiment of the present invention two at high pressure phase below in conjunction with Figure 21, at high pressure phase, booster circuit 2 does not work, and the first switching device S1 turns off always; Second switch device S2 in reduction voltage circuit 4 and the 3rd switching device S3 is triggered by high-frequency signal.Equally, at the positive half cycle of alternating voltage, the 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 conducting, the 5th switching device S5 and the 6th switching device S6 turns off; At the negative half period of alternating voltage, the 4th switching device S4 in inverter circuit 6 and the 7th switching device S7 turns off, the 5th switching device S5 and the 6th switching device S6 conducting.Because definition high pressure phase is direct voltage U dcbe not less than line voltage peak value U ac (max)situation, therefore there is not U dcbe less than | U ac (t)| situation, the voltage changer of the embodiment of the present invention two at the current direction figure of high pressure phase as shown in Figure 13 to Figure 16.
As can be seen from Figure 21, the first intermediate voltage U d1size equal direct voltage U dc, the second intermediate voltage U d2be the absolute value voltage of filtered sine wave AC voltage, the sine wave AC voltage that the absolute value voltage of this filtered sine wave AC voltage generates standard after the commutation of inverter circuit 6 power frequency is supplied to AC load 8.
It should be noted that, above-mentioned high-frequency pulse signal is pulse signal within the scope of KHz or pulse width modulating signal, and the frequency of power frequency pulse signal is 50Hz or 60Hz.
Can learn, at U from the voltage changer of the invention described above embodiment two and operation method thereof dcbe not less than | U ac (t)| during, booster circuit 2 does not work; At U dcbe less than | U ac (t)| during, booster circuit 2 just works, and voltage converter circuit is simple, and dc voltage operation wide ranges, voltage utilization are high.And at U dcbe not less than | U ac (t)| during, booster circuit 2 does not work, and therefore conversion efficiency is improved.
Further, from voltage changer and the operation method thereof of the invention described above embodiment two, can learn, when booster circuit does not work, interchange continuous current circuit and DC side disconnect completely, thus effectively inhibit common mode leakage current; And when booster circuit works, although exchange continuous current circuit to comprise DC side, but under the first inductance L 1 in booster circuit 2 and the acting in conjunction of the first energy storage filter unit 3, can high fdrequency component preferably in filtering direct voltage, thus inhibit high-frequency leakage current.
Further, the first energy storage filter unit 3 and reduction voltage circuit 4 adopt symmetrical circuit structure, inhibit by DC power supply 1 leakage current that flows through of parasitic capacitance over the ground, improve the functional reliability of voltage changer, improve the performance of voltage changer electromagnetism interference.
In addition, the corresponding part of the first energy storage filter unit 3, reduction voltage circuit 4 selects electric property and the identical electronic devices and components of parameter and synchronization action, thus further suppress by DC power supply 1 performance of leakage current, the functional reliability that improve voltage changer and voltage changer electromagnetism interference that flows through of parasitic capacitance over the ground.
In addition, in each work period of alternating voltage, second switch device S2 is identical with the triggering signal of the 3rd switching device S3, and the 3rd diode D3 and the 4th diode D4 is connected in series between the positive direct-current bus of voltage changer and negative DC bus, therefore second switch device S2 and the 3rd switching device S3 can select the switching tube that tube voltage drop is lower, 3rd diode D3 and the 4th diode D4 can select the diode that tube voltage drop is lower, improves conversion efficiency, reduces cost; Meanwhile, the 4th switching device S4 is in power frequency operating state to the 7th switching device S7, therefore can select the switching tube at a slow speed that conduction voltage drop is lower, thus further increase conversion efficiency, reduce cost.
The circuit diagram of the embodiment of the present invention three as shown in figure 22.
Compared with the embodiment of the present invention two (physical circuit as shown in figure 12), the circuit difference of embodiment three is that the first energy storage filter unit 3 is the first electric capacity, is not adopt symmetrical structure; In reduction voltage circuit 4, a buck circuit and the 2nd buck circuit share a diode, i.e. the 3rd diode D3; Therefore in embodiment three, the pressure drop ratio embodiment two of bearing required for the 3rd diode D3 larger.
The operation method of the voltage changer of embodiment three is identical with the operation method of embodiment two, repeats no more herein.
In sum, relative to prior art, the voltage changer dc voltage operation scope that the embodiment of the present invention provides is wider, conversion efficiency is higher, cost is low and effectively can suppress leakage current.
Being described in detail the embodiment of the present invention above, applying embodiment herein to invention has been elaboration, the explanation of above embodiment just understands equipment of the present invention and method for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention.

Claims (13)

1. a voltage changer, is supplied to AC load for converting direct-current voltage into alternating-current voltage DC power supply exported, it is characterized in that, this voltage changer comprises booster circuit, the first energy storage filter unit, reduction voltage circuit, inverter circuit and by-pass unit;
The input of described booster circuit is connected in the two ends of DC power supply in parallel, between the output that described first energy storage filter unit, reduction voltage circuit and inverter circuit order is connected in described booster circuit in parallel and AC load, the first end of described by-pass unit is connected with the positive pole of DC power supply, the output of its second termination booster circuit;
The direct voltage that described booster circuit is used for DC power supply exports is converted to higher direct voltage and exports;
Described first energy storage filter unit is used for the high fdrequency component in the higher direct voltage that described in filtering, booster circuit exports and generates the first intermediate voltage exporting;
Described first intermediate voltage is converted to the absolute value voltage of sine wave AC voltage by described reduction voltage circuit;
The absolute value voltage of the sine wave AC voltage that described reduction voltage circuit exports by inverter circuit carries out power frequency commutation generation sinusoidal voltage and is supplied to AC load;
Described by-pass unit is used for during described direct voltage is not less than the absolute value of line voltage instantaneous value, by described booster circuit bypass.
2. voltage changer according to claim 1, is characterized in that,
Described booster circuit comprises the first inductance, the second diode, the first switching device, the described first end of the first inductance is connected with the positive pole of DC power supply, second end of the first inductance is connected with the first end of the first switching device with the anode of the second diode, the negative pole of the second termination DC power supply of the first switching device, the negative electrode of the second diode connects the second end of described by-pass unit;
Described inverter circuit comprises and is connected in series by the 4th switching device and the 5th switching device the first branch road of being formed and is connected in series by the 6th switching device and the 7th switching device the second branch road formed, first branch road and the second branch road are connected in parallel on the output of described reduction voltage circuit respectively, the tie point of the 4th switching device and the 5th switching device draws the first end connecing AC load, and the tie point of the 6th switching device and the 7th switching device draws the second end connecing AC load.
3. voltage changer according to claim 2, is characterized in that, described first energy storage filter unit comprises the first electric capacity, the negative electrode of the first termination second diode of the first electric capacity, the negative pole of the second termination DC power supply of the first electric capacity; Described reduction voltage circuit comprises a buck circuit, one buck circuit comprises second switch device, the 3rd diode, the second inductance, the first end of second switch device is connected with the first end of the first electric capacity, second end of second switch device is connected with the first end of the second inductance with the negative electrode of the 3rd diode, the anode of the 3rd diode connects the second end of the first electric capacity, and the second end of the second inductance is connected with described inverter circuit.
4. voltage changer according to claim 3, it is characterized in that, described reduction voltage circuit also comprises the 2nd buck circuit, 2nd buck circuit comprises the 3rd switching device, the 3rd inductance, second end of the first termination first electric capacity of the 3rd switching device, second termination of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 3rd diode, and the second end of the 3rd inductance is connected with described inverter circuit.
5. voltage changer according to claim 4, is characterized in that, second switch device and the 3rd switching device, the second inductance and the 3rd inductance are respectively the electronic devices and components of same model.
6. voltage changer according to claim 4, it is characterized in that, described first energy storage filter unit also comprises the second electric capacity be connected with the first capacitances in series, second end of the first electric capacity is connected with the first end of the second electric capacity and tie point is used for producing the midpoint potential of described first intermediate voltage, the negative pole of the second termination DC power supply of the second electric capacity; Described 2nd buck circuit also comprises the 4th diode, second end of the first termination second electric capacity of the 3rd switching device, second termination of the 3rd switching device is connected with the first end of the 3rd inductance with the anode of the 4th diode, and the negative electrode of the 4th diode is connected with the anode of the 3rd diode and tie point connects the midpoint potential of described first intermediate voltage.
7. voltage changer according to claim 6, it is characterized in that, described first electric capacity and the second electric capacity, second switch device and the 3rd switching device, the 3rd diode and the 4th diode, the second inductance and the 3rd inductance are respectively the electronic devices and components of same model.
8. voltage changer according to claim 1, is characterized in that, described by-pass unit is the first diode, and the anode of described first diode connects the positive pole of DC power supply, and the negative electrode of described first diode connects the output of booster circuit.
9. voltage changer according to any one of claim 1 to 8, it is characterized in that, this voltage changer also comprises the second energy storage filter unit be connected between reduction voltage circuit and inverter circuit, and the high fdrequency component in the absolute value voltage of the sine wave AC voltage exported for reduction voltage circuit described in filtering also generates the second intermediate voltage and exports to described inverter circuit.
10. the operation method based on voltage changer according to claim 3, it is characterized in that, when described direct voltage is less than line voltage peak value, size between the absolute value judging direct voltage and line voltage instantaneous value, if direct voltage is not less than the absolute value of line voltage instantaneous value, first switching device turns off, and second switch device is by high-frequency signal trigger action; If direct voltage is less than the absolute value of line voltage instantaneous value, the first switching device by high-frequency signal trigger action, second switch break-over of device; When described direct voltage is not less than line voltage peak value, the first switching device turns off, and second switch device is by high-frequency signal trigger action.
The operation method of 11. voltage changers according to claim 10, is characterized in that, at the positive half cycle of alternating voltage, and the 4th switching device and the 7th switch device conductive, the 5th switching device and the 6th switching device turn off; At the negative half period of alternating voltage, the 4th switching device and the 7th switching device turn off, the 5th switching device and the 6th switch device conductive.
12. 1 kinds of operation methods based on the voltage changer described in claim 5 or 7, it is characterized in that, when described direct voltage is less than line voltage peak value, size between the absolute value judging direct voltage and line voltage instantaneous value, if direct voltage is not less than the absolute value of line voltage instantaneous value, first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action; If direct voltage is less than the absolute value of line voltage instantaneous value, the first switching device by high-frequency signal trigger action, second switch device and the 3rd switch device conductive; When described direct voltage is not less than line voltage peak value, the first switching device turns off, and second switch device and the 3rd switching device are by synchronous high-frequency signal trigger action.
The operation method of 13. voltage changers according to claim 12, is characterized in that, at the positive half cycle of alternating voltage, and the 4th switching device and the 7th switch device conductive, the 5th switching device and the 6th switching device turn off; At the negative half period of alternating voltage, the 4th switching device and the 7th switching device turn off, the 5th switching device and the 6th switch device conductive.
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