Converter device and control method thereof
阅读说明：本技术 一种变换器装置及其控制方法 (Converter device and control method thereof ) 是由 徐君 庄加才 谷雨 顾亦磊 于 2018-06-15 设计创作，主要内容包括：本申请公开了一种变换器装置及其控制方法。所述变换器装置的主电路包括功率解调器以及多个具有升降压功能的功率调制器；各功率调制器的输入端分别连接至少一个直流电源,所有功率调制器的输出端串联后接入所述功率解调器的输入端,所述功率解调器的输出端接入电网或交流负载。所述变换器装置的控制电路包括功率调制器控制单元和功率解调器控制单元,所述功率调制器控制单元用于控制所述功率调制器输出电压频率为2*f的馒头波,f为电网电压频率或交流负载所需电压的频率；所述功率解调器控制单元用于控制所述功率解调器将所有功率调制器串联输出的总电压解调成电压频率为f的正弦交流电,以提高系统整体效率。(The application discloses a converter device and a control method thereof. The main circuit of the converter device comprises a power demodulator and a plurality of power modulators with a voltage boosting and reducing function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load. The control circuit of the converter device comprises a power modulator control unit and a power demodulator control unit, wherein the power modulator control unit is used for controlling the power modulator to output steamed bread waves with voltage frequency of 2 x f, and f is the voltage frequency of a power grid or the frequency of voltage required by an alternating current load; the power demodulator control unit is used for controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f so as to improve the overall efficiency of the system.)
1. A converter device is characterized in that a main circuit of the converter device comprises a power demodulator and a plurality of power modulators with a voltage boosting and reducing function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load;
the control circuit of the converter device comprises a power modulator control unit and a power demodulator control unit, wherein the power modulator control unit is used for controlling the power modulator to output steamed bread waves with voltage frequency of 2 x f, and f is the voltage frequency of a power grid or the frequency of voltage required by an alternating current load; the power demodulator control unit is used for controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f.
2. The converter arrangement of claim 1, wherein said power demodulator comprises a full bridge circuit, a capacitor connected to an input side of said full bridge circuit, and a filter circuit connected to an output side of said full bridge circuit; the full-bridge circuit is provided with a first bridge arm and a second bridge arm;
the power demodulator control unit is used for controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched on and the upper tube of the second bridge arm and the lower tube of the first bridge arm to be switched off when the voltage of a power grid or the voltage required by an alternating current load is positive; and when the voltage of the power grid or the voltage required by the alternating current load is negative, controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched off, and switching on the upper tube of the second bridge arm and the lower tube of the first bridge arm.
3. The converter arrangement according to claim 1, characterized in that the power modulator is a non-isolated power modulator.
4. A converter arrangement according to claim 3, characterized in that the non-isolated power modulator is a Buck-Boost circuit, a Cuk circuit, a Sepic circuit or a Zeta circuit.
5. The converter arrangement according to claim 1, characterized in that the direct current source is a photovoltaic module or a battery.
6. The converter device according to claim 5, wherein when the dc power source is a photovoltaic module, the power modulator control unit is further configured to control the power modulator to perform MPPT control.
7. The converter arrangement according to claim 6, characterized in that the k-th power modulator in the converter arrangement is called power modulator k; k is 1,2,3, …, n; n is the total number of the power modulators; the photovoltaic module, the voltage controller and the power controller corresponding to the power modulator k are respectively called a photovoltaic module k, a voltage controller k and a power controller k;
the power modulator control unit is specifically configured to:
sampling value v of input voltage according to power modulator kdckAnd the output current sampling value i of the photovoltaic module kPVkAnd the control power modulator k carries out MPPT control on the photovoltaic component k to obtain an input voltage reference value V of the power modulator kPVk*；
From voltage controller k with VPVkA and vdckAs input, the output power amplitude P of the power modulator k is calculatedk；
According to formula Pk_REF＝Pksin2Theta is calculated to obtain the output power reference value P of the power modulator kk_REF(ii) a Wherein θ is the phase angle;
according to formula Pk_FDB＝vok*idcCalculating to obtain the feedback value P of the k output power of the power modulatork_FDBWherein v isokAnd idcThe sampling values of the voltage of an output capacitor of the power modulator k and the sampling value of the input current of the power demodulator are respectively;
by power controller k with Pk_REFAnd Pk_FDBAs input, the duty cycle d of the power modulator is calculatedk；
According to duty cycle dkAnd calculating to obtain a switching tube driving signal of the power modulator k.
8. The converter device according to claim 1, wherein the power modulator control unit and the power demodulator control unit perform information interaction by wired communication or wireless communication, wherein the wired communication includes power line carrier communication, communication cable communication, optical fiber communication or field bus communication.
9. A control method of a converter device is characterized in that the converter device comprises a power demodulator and a plurality of power modulators with a voltage boosting and reducing function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load;
the inverter device control method includes:
controlling each power modulator to output steamed bread waves with voltage frequency of 2 x f, wherein f is the frequency of the voltage of a power grid or the frequency of the voltage required by an alternating current load;
and controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f.
10. The converter apparatus control method according to claim 9, wherein the power demodulator includes a full bridge circuit, a capacitor connected to an input side of the full bridge circuit, and a filter circuit connected to an output side of the full bridge circuit; the full-bridge circuit is provided with a first bridge arm and a second bridge arm;
correspondingly, the controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into a sinusoidal alternating current with a voltage frequency f specifically includes:
identifying the positive and negative of the power grid voltage or the voltage required by the alternating current load;
when the voltage of a power grid or the voltage required by an alternating current load is positive, controlling an upper tube of a first bridge arm and a lower tube of a second bridge arm to be switched on, and switching off the upper tube of the second bridge arm and the lower tube of the first bridge arm;
and when the voltage of the power grid or the voltage required by the alternating current load is negative, controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched off, and switching on the upper tube of the second bridge arm and the lower tube of the first bridge arm.
Technical Field
The present invention relates to the field of power conversion technologies, and in particular, to a converter apparatus and a control method thereof.
Background
The output of a single dc power supply is often insufficient to provide the actual voltage and power requirements, so that a plurality of dc power supplies are required to be connected in series and parallel to form a whole to meet the design requirements. As shown in fig. 1, in a conventional power generation system, a DC/DC converter is configured for each DC power source, output terminals of all DC/DC converters are connected in series and then connected to an inverter, and the inverter modulates a total voltage output by all DC/DC converters in series into a sinusoidal alternating current for transmitting power to a power grid or supplying power to an ac load.
However, fig. 1 is a two-stage system, the DC/DC converter and the inverter are both controlled by PWM (Pulse Width Modulation), and the internal switching tube thereof works in a high-frequency switching state, so that the switching loss is large, which results in low overall efficiency of the system.
Disclosure of Invention
In view of the above, the present invention provides a converter apparatus and a control method thereof to improve the overall efficiency of the system.
A converter device comprises a main circuit, a plurality of main circuits and a plurality of power modulators, wherein the power modulators have a voltage boosting and reducing function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load;
the control circuit of the converter device comprises a power modulator control unit and a power demodulator control unit, wherein the power modulator control unit is used for controlling the power modulator to output steamed bread waves with voltage frequency of 2 x f, and f is the voltage frequency of a power grid or the frequency of voltage required by an alternating current load; the power demodulator control unit is used for controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f.
Optionally, the power demodulator includes a full bridge circuit, a capacitor connected to an input side of the full bridge circuit, and a filter circuit connected to an output side of the full bridge circuit; the full-bridge circuit is provided with a first bridge arm and a second bridge arm;
the power demodulator control unit is used for controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched on and the upper tube of the second bridge arm and the lower tube of the first bridge arm to be switched off when the voltage of a power grid or the voltage required by an alternating current load is positive; and when the voltage of the power grid or the voltage required by the alternating current load is negative, controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched off, and switching on the upper tube of the second bridge arm and the lower tube of the first bridge arm.
Optionally, the power modulator is a non-isolated power modulator.
Optionally, the non-isolated power modulator is a Buck-Boost circuit, a Cuk circuit, a Sepic circuit or a Zeta circuit.
Optionally, the direct current power supply is a photovoltaic module or a storage battery.
Optionally, when the dc power supply is a photovoltaic module, the power modulator control unit is further configured to control the power modulator to perform MPPT control.
Optionally, the kth power modulator in the converter apparatus is referred to as power modulator k; k is 1,2,3, …, n; n is the total number of the power modulators; the photovoltaic module, the voltage controller and the power controller corresponding to the power modulator k are respectively called a photovoltaic module k, a voltage controller k and a power controller k;
the power modulator control unit is specifically configured to:
sampling value v of input voltage according to power modulator kdckAnd the output current sampling value i of the photovoltaic module kPVkAnd the control power modulator k carries out MPPT control on the photovoltaic component k to obtain an input voltage reference value V of the power modulator kPVk*；
From voltage controller k with VPVkA and vdckAs input, the output power amplitude P of the power modulator k is calculatedk；
According to formula Pk_REF＝Pksin2Theta is calculated to obtain the output power reference value P of the power modulator kk_REF(ii) a Wherein theta isIs a phase angle;
according to formula Pk_FDB＝vok*idcCalculating to obtain the feedback value P of the k output power of the power modulatork_FDBWherein v isokAnd idcThe sampling values of the voltage of an output capacitor of the power modulator k and the sampling value of the input current of the power demodulator are respectively;
by power controller k with Pk_REFAnd Pk_FDBAs input, the duty cycle d of the power modulator is calculatedk；
According to duty cycle dkAnd calculating to obtain a switching tube driving signal of the power modulator k.
Optionally, the power modulator control unit and the power demodulator control unit perform information interaction in a wired communication or wireless communication manner, where the wired communication includes power line carrier communication, communication cable communication, optical fiber communication, or field bus communication.
A converter apparatus control method, the converter apparatus includes a power demodulator and a plurality of power modulators having a step-up/step-down function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load;
the inverter device control method includes:
controlling each power modulator to output steamed bread waves with voltage frequency of 2 x f, wherein f is the frequency of the voltage of a power grid or the frequency of the voltage required by an alternating current load;
and controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f.
Optionally, the power demodulator includes a full bridge circuit, a capacitor connected to an input side of the full bridge circuit, and a filter circuit connected to an output side of the full bridge circuit; the full-bridge circuit is provided with a first bridge arm and a second bridge arm;
correspondingly, the controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into a sinusoidal alternating current with a voltage frequency f specifically includes:
identifying the positive and negative of the power grid voltage or the voltage required by the alternating current load;
when the voltage of a power grid or the voltage required by an alternating current load is positive, controlling an upper tube of a first bridge arm and a lower tube of a second bridge arm to be switched on, and switching off the upper tube of the second bridge arm and the lower tube of the first bridge arm;
and when the voltage of the power grid or the voltage required by the alternating current load is negative, controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched off, and switching on the upper tube of the second bridge arm and the lower tube of the first bridge arm.
According to the technical scheme, the power modulators are controlled to output the steamed bread waves with the voltage frequency of 2 x f, and the power demodulators are used for modulating the total voltage output by all the power modulators in series into the sine alternating current with the voltage frequency of f. And f is power frequency sine alternating current obtained by modulating the power demodulator by the power demodulator, and the internal switching tube works in a power frequency switching state when the power demodulator modulates the power frequency sine alternating current.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a power generation system disclosed in the prior art;
FIG. 2 is a schematic diagram of a main circuit structure of a converter device according to an embodiment of the present invention;
fig. 3 is a control block diagram of a power modulator k according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a Buck-Boost circuit topology structure disclosed in the embodiment of the present invention;
FIG. 5 is a schematic diagram of a Buck-Boost circuit topology according to another embodiment of the present invention;
FIG. 6 is a schematic diagram of a Cuk circuit topology structure disclosed in the embodiments of the present invention;
FIG. 7 is a schematic diagram of a Sepic circuit topology structure disclosed in the embodiment of the present invention;
FIG. 8 is a schematic diagram of a Zeta circuit topology according to an embodiment of the present invention;
FIG. 9 is a flowchart of a method for controlling a converter apparatus according to an embodiment of the present invention;
fig. 10 is a flowchart of a power demodulator control method according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a converter device, as shown in fig. 2, a main circuit of the converter device comprises a power demodulator and a plurality of power modulators with a voltage boosting and reducing function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid (namely, a grid-connected state) or an alternating current load (namely, an off-grid state). Wherein, the direct current power supply can be a photovoltaic module, a storage battery or other energy storage devices.
The control circuit of the converter device comprises a power modulator control unit and a power demodulator control unit, wherein the power modulator control unit is used for controlling the power modulator to output steamed bread waves with voltage frequency of 2 × f (when the system is designed, each power modulator can be provided with an independent power modulator control unit, or can be grouped into a plurality of power modulators, each group is provided with an independent power modulator control unit), and f is the frequency of the power grid voltage or the frequency of the voltage required by an alternating current load; the power demodulator control unit is used for controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f. The voltage required by the power grid and the voltage required by the alternating current load are both sinusoidal alternating current.
Specifically, the steamed bread wave is equivalent to a wave form of sine alternating current after the sine alternating current takes an absolute value, and the frequency of the wave form is equal to twice of the frequency of the sine alternating current. The embodiment of the invention controls all power modulators to output the steamed bread waves with the voltage frequency of 2 f, and because the output ends of all power modulators are connected in series, the voltages output by all power modulators are superposed to form the steamed bread waves with the amplitude equal to the sum of the amplitudes of the output voltages of all power modulators and the voltage frequency of 2 f, which is called as the total voltage output by all power modulators in series.
The demodulation of the power demodulator is specifically that the state of a switch tube in the power demodulator is switched when the voltage of a power grid or the voltage required by an alternating current load is zero, so that the total voltage output by all the power modulators in series is demodulated into sinusoidal alternating current with the voltage frequency f. The power frequency voltage is the unified standard voltage of the power industry and the electrical equipment specified by the state, in order to obtain the power frequency sine alternating current, each power modulator needs to output double power frequency steamed bread waves, the power demodulator needs to modulate the double power frequency steamed bread waves output by all the power modulators in series into the power frequency sine alternating current, and when the power demodulator modulates the power frequency sine alternating current, the internal switching tube works in a power frequency switching state.
Optionally, the power demodulator may adopt a topology as shown in fig. 2, including: the circuit comprises a full-bridge circuit, a capacitor connected to the input side of the full-bridge circuit and a filter circuit connected to the output side of the full-bridge circuit, wherein the full-bridge circuit is provided with a first bridge arm and a second bridge arm. The control strategy is as follows: when the voltage of a power grid or the voltage required by an alternating current load is greater than 0, controlling an upper tube S3 of the first bridge arm and a lower tube S2 of the second bridge arm to be switched on, and switching off an upper tube S1 of the second bridge arm and a lower tube S4 of the first bridge arm; and when the power grid voltage or the voltage required by the alternating current load is less than 0, controlling the upper tube S3 of the first bridge arm and the lower tube S2 of the second bridge arm to be turned off, and controlling the upper tube S1 of the second bridge arm and the lower tube S4 of the first bridge arm to be turned on.
Optionally, in any of the converter apparatuses disclosed above, when the dc Power supply is a photovoltaic module, the Power modulator control unit is further configured to control the Power modulator to perform MPPT (Maximum Power point tracking) control, so as to improve a photovoltaic utilization rate and avoid a hot spot effect.
Fig. 3 shows the operation process of the power modulator control unit controlling the power modulator to perform MPPT control and controlling the power modulator to output a double power frequency time wave, which is described as follows:
for the sake of convenience of description, the kth power modulator in the converter arrangement will be referred to as power modulator k hereinafter; k is 1,2,3, …, n; n is the total number of the power modulators; the photovoltaic module, the voltage controller and the power controller corresponding to the power modulator k are respectively called a photovoltaic module k, a voltage controller k and a power controller k.
Sampling value v of input voltage according to power modulator kdckAnd the output current sampling value i of the photovoltaic module kPVkAnd the control power modulator k carries out MPPT control on the photovoltaic component k to obtain an input voltage reference value V of the power modulator kPVk*；
V is controlled by a voltage controller k (the voltage controller k can adopt a proportional controller, a proportional integral controller or a proportional resonant controller, etc.)PVkA and vdckAs input, the output power amplitude P of the power modulator k is calculatedk；
According to formula Pk_REF＝Pksin2Theta is calculated to obtain the output power reference value P of the power modulator kk_REF(ii) a The phase angle theta is obtained by performing phase-locked control on the power grid voltage;
according to formula Pk_FDB＝vok*idcCalculating to obtain the output power feedback value P of the power modulatork_FDBWherein v isokAnd idcThe sampling values of the output capacitor voltage of the power modulator k and the input current of the power demodulator are respectively;
the power controller k (the power controller k can adopt a proportional controller, a proportional integral controller or a proportional resonant controller, etc.) and the power controller k can control the power of the power converter k to be Pk_REFAnd Pk_FDBAs input, the duty cycle d of the power modulator is calculatedk；
According to duty cycle dkThe calculation results in the switch tube driving signal of the power modulator, and the power modulator k outputs double power frequency time wave.
Alternatively, in any of the inverter devices disclosed above, the power modulator may be a non-isolated power modulator, or an isolated power modulator, but in view of the fact that the former can reduce the system cost and improve the overall efficiency, the present embodiment recommends the use of a non-isolated power modulator. The non-isolated power modulator may be a Buck-Boost circuit, a Cuk circuit, a Sepic circuit, a Zeta circuit, or the like, without limitation.
The Buck-Boost circuit may adopt a topology structure as shown in fig. 4, and includes a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, a fourth switching tube Q4, a first inductor L1, an input capacitor C1, and an output capacitor C2, where: the positive electrode of C1 is connected with the first end of Q1; a second terminal of Q1, one end of L1 and a first end of Q2; the other end of the L1 is connected with the first ends of the Q3 and the Q4; the second end of the Q4 is connected with the positive pole of the C2; a second end of Q2 terminates the negative terminal of C1 and a second end of Q3; the second end of the Q3 is connected with the negative pole of the C2.
Alternatively, the Buck-Boost circuit may also adopt a topology as shown in fig. 5, and include a fifth switching tube Q5, a second inductor L2, a first diode D1, an input capacitor C1, and an output capacitor C2, where: the positive electrode of C1 is connected with the first end of Q5; a second terminal of Q5, one end of L2 and the cathode of D1; the anode of D1 is connected with the anode of C2; the other end of L2 terminates the negative poles of C2 and C1.
The Cuk circuit may adopt a topology as shown in fig. 6, and includes a third inductor L3, a fourth inductor L4, a third capacitor C3, a sixth switching tube Q6, a second diode D2, an input capacitor C1, and an output capacitor C2, where: the positive electrode of the C1 is connected with one end of the L3; the other end of the L3 is connected with one end of the C3 and the first end of the Q6; the other end of the C3 is connected with one end of the L4 and the anode of the D2; the other end of the L4 is connected with the anode of the C2; the cathode of C2 is connected with the cathode of D2, the second end of Q6 and the cathode of C1.
The Sepic circuit may adopt a topology structure as shown in fig. 7, and includes a fifth inductor L5, a sixth inductor L6, a seventh switching tube Q7, a fourth capacitor C4, a third diode D3, an input capacitor C1, and an output capacitor C2, where: the positive electrode of the C1 is connected with one end of the L5; the other end of the L5 is connected with one end of the C4 and the first end of the Q7; the other end of the C4 is connected with one end of the L6 and the anode of the D3; the cathode of the D3 is connected with the anode of the C2; the cathode of C2 is connected to the other end of L6, the second end of Q7 and the cathode of C1.
The Zeta circuit may adopt a topology as shown in fig. 8, and includes a fifth capacitor C5, an eighth switching tube Q8, a seventh inductor L7, an eighth inductor L8, a fourth diode D4, an input capacitor C1, and an output capacitor C2, where: the positive electrode of C1 is connected with the first end of Q8; a second terminal of Q8, C5, and L8; the other end of the C5 is connected with one end of the L7 and the cathode of the D4; the other end of the L7 is connected with the anode of the C2; the cathode of C2 is connected with the anode of D4, the other end of L8 and the cathode of C1.
The switching tube shown in fig. 4 to 8 may be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor) with a diode, or another Semiconductor device. When the switch tube is an MOSFET, the first end of the switch tube is the drain electrode of the MOSFET, and the second end of the switch tube is the source electrode of the MOSFET; when the switch tube is an IGBT with a body diode, the first end of the switch tube is a collector electrode of the IGBT, and the second end of the switch tube is an emitter electrode of the IGBT with the body diode.
Optionally, in any of the converter apparatuses disclosed above, information interaction is required between the power modulator control unit and the power demodulator control unit, for example, the dc power state information acquired by the power modulator control unit is sent to the power demodulator control unit for system power adjustment and monitoring, and the power demodulator control unit sends the grid related information to the power modulator control unit for power control. The interaction mode can be wired communication or wireless communication; the wired communication may be, for example, but not limited to, power line carrier communication, communication cable communication, optical fiber communication, field bus communication, or the like; the wireless communication may be, for example, bluetooth communication or radio frequency communication, etc., but is not limited thereto.
Corresponding to the embodiment, the invention also discloses a photovoltaic inverter control method. The main circuit of the photovoltaic inverter is shown in fig. 2 and comprises a power demodulator and a plurality of power modulators with a buck-boost function; the input end of each power modulator is respectively connected with at least one direct current power supply, the output ends of all the power modulators are connected in series and then connected to the input end of the power demodulator, and the output end of the power demodulator is connected to a power grid or an alternating current load. As shown in fig. 9, the photovoltaic inverter control method includes:
step S01: controlling each power modulator to output steamed bread waves with voltage frequency of 2 x f, wherein f is the frequency of the voltage of a power grid or the frequency of the voltage required by an alternating current load;
step S02: and controlling the power demodulator to demodulate the total voltage output by all the power modulators in series into sinusoidal alternating current with the voltage frequency f.
Optionally, the power demodulator includes a full bridge circuit, a capacitor connected to an input side of the full bridge circuit, and a filter circuit connected to an output side of the full bridge circuit; the full bridge circuit has a first leg and a second leg. Correspondingly, the step S02 specifically includes:
step S021: identifying the positive and negative of the power grid voltage or the voltage required by the alternating current load; when the grid voltage or the voltage required by the alternating current load is positive, the step S022 is carried out; when the grid voltage or the voltage required by the alternating current load is negative, the step S023 is carried out;
step S022: controlling an upper pipe of the first bridge arm and a lower pipe of the second bridge arm to be switched on, and switching off the upper pipe of the second bridge arm and the lower pipe of the first bridge arm; and then returns to step S021.
Step S023: controlling the upper tube of the first bridge arm and the lower tube of the second bridge arm to be switched off, and switching on the upper tube of the second bridge arm and the lower tube of the first bridge arm; and then returns to step S021.
Optionally, the power modulator is a non-isolated power modulator.
In conclusion, the invention controls each power modulator to output the steamed bread waves with the voltage frequency of 2 x f, and then modulates the total voltage output by all the power modulators in series into the sine alternating current with the voltage frequency of f by using the power demodulator. And f is power frequency sine alternating current obtained by modulating the power demodulator by the power demodulator, and the internal switching tube works in a power frequency switching state when the power demodulator modulates the power frequency sine alternating current. In addition, the output voltage and the current polarity of each power modulator are positive, so that each power modulator can be bypassed by a bypass diode when in fault, and the current has a zero point, so that the arc extinction is easy.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.