CN109728739B - Voltage regulating circuit and inverter system - Google Patents
Voltage regulating circuit and inverter system Download PDFInfo
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- CN109728739B CN109728739B CN201811619706.0A CN201811619706A CN109728739B CN 109728739 B CN109728739 B CN 109728739B CN 201811619706 A CN201811619706 A CN 201811619706A CN 109728739 B CN109728739 B CN 109728739B
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Abstract
The application provides a voltage regulating circuit and an inverter system. The voltage regulating circuit comprises a first voltage regulator tube, a second voltage regulator tube, a voltage stabilizing resistor, a circuit switch, a first capacitor and a second capacitor; the first voltage-regulator tube and the first capacitor are connected between the first node and the second node in parallel; the voltage stabilizing resistor and the second capacitor are connected between the second node and the third node in parallel; the second voltage-regulator tube and the circuit switch are connected in series between the first node and the second node; the voltage stabilizing value of the first voltage stabilizing tube is different from that of the second voltage stabilizing tube; the voltage between the first node and the third node is a bus voltage. The technical scheme that this application provided can be applied to among the photovoltaic power generation system, can adjust the driving voltage of inverter switch tube through voltage regulating circuit, specifically, when the inverter starts, provides less driving voltage for the switch tube of inverter to reduce the peak voltage that the switch tube bore, when power generation system high power operation, provide great driving voltage for the switch tube, thereby reduce the heat loss.
Description
Technical Field
The application relates to the technical field of power electronics, in particular to a voltage regulating circuit and an inverter system.
Background
MOSFETs and IGBTs are currently the mainstream controlled switching devices controlled by voltage, and are widely used in photovoltaic power generation systems. Fig. 1 is a structural diagram of a current photovoltaic power generation system, as shown in fig. 1, in the photovoltaic power generation system, electric energy generated by a battery panel is transmitted to a bus capacitor C0 through conversion of a DC/DC isolation power supply, and is converted into alternating current through a DC/AC inverter and is transmitted to a power grid, wherein the inverter forms a topology structure through a plurality of switching devices and parasitic inductors, and the conversion of direct current into alternating current is realized by controlling the switching states of the switching devices.
Fig. 2 is a voltage-current-power relation graph of a current photovoltaic power generation system. As shown in fig. 2, the conventional photovoltaic power generation system has characteristics of large open-circuit voltage and small current, low full-load output voltage and large current, and thus causes small thermal stress when voltage stress is large and large thermal stress when voltage stress is small in a semiconductor device such as a controlled switch used in a circuit such as an inverter. In addition, in order to improve the power density of the battery panel, the open circuit voltage of the photovoltaic power generation system is increasing in recent years, so that the input voltage of the inverter is also increasing, the voltage stress borne by the semiconductor device is increasing, the performance requirements of the semiconductor device are becoming more and more strict, and the selectivity of the semiconductor device is becoming lower and more.
In addition, because the parasitic inductance exists in the inverter, when the switching device is turned on or turned off, a peak voltage is generated, and the larger the voltage at two ends of the parasitic inductance is, the larger the peak voltage is, so that the switching device may be damaged, and the stable operation of the system may be affected. At present, a method can absorb part of the voltage stress by introducing an absorption circuit into the system, so as to reduce the peak voltage, but additional heat is generated in the process of absorbing the voltage stress, so that the system efficiency is reduced, and additional heat dissipation measures are required. While another approach reduces the bus voltage of the switching device by closed-loop control to reduce the spike voltage, it is difficult to arrange in an open-loop photovoltaic power generation system.
Disclosure of Invention
The application provides a voltage regulating circuit and an inverter system, which can reduce spike voltage generated in an inverter and reduce heat loss.
In a first aspect, the present application provides a voltage regulation circuit, which specifically includes: the circuit comprises a first voltage-regulator tube, a second voltage-regulator tube, a voltage-regulator resistor, a circuit switch, a first capacitor and a second capacitor. The first voltage regulator tube and the first capacitor are connected between the first node and the second node in parallel; the voltage stabilizing resistor and the second capacitor are connected between the second node and the third node in parallel; the second voltage-regulator tube and the circuit switch are connected in series between the first node and the second node, and a circuit formed by connecting the second voltage-regulator tube and the circuit switch in series is connected with the first voltage-regulator tube in parallel; the voltage stabilizing value of the first voltage stabilizing tube is larger than that of the second voltage stabilizing tube; the voltage between the first node and the third node is a bus voltage.
The voltage regulating circuit can be applied to a photovoltaic power generation system to provide variable driving voltage for a switching tube in an inverter, when the inverter starts to start, the switching tube bears larger peak voltage due to higher open-circuit voltage and smaller output power of the photovoltaic power generation system, and at the moment, the switching speed of the switching tube is reduced by providing smaller driving voltage for the switching tube and controlling the on-off state of a circuit switch so as to reduce the peak voltage borne by the switching tube; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
In one possible approach, the circuit switch includes a switching element and a switch control circuit for controlling the closing and opening of the switching element.
Therefore, the switch control circuit can control the on and off of the switch element, and the voltage regulating process of the voltage regulating circuit is completed.
In one possible approach, the second node is a zero potential node, the bus voltage is a positive voltage at the first node relative to the second node, and the bus voltage is a negative voltage at the third node relative to the second node.
Therefore, the positive voltage for driving the switch tube can be directly adjusted by setting the open and close states of the circuit switch, and the voltage regulation of the driving voltage of the switch tube is realized.
In one possible approach, the second node is a zero potential node, the bus voltage is a negative voltage at the first node relative to the second node, and the bus voltage is a positive voltage at the third node relative to the second node.
Therefore, the negative voltage can be adjusted by setting the open and close states of the circuit switch so as to indirectly adjust the positive voltage for driving the switch tube and realize the voltage regulation of the driving voltage of the switch tube.
In a possible mode, the second voltage regulator tube is connected with the first node, and the circuit switch is connected with the second node, or the second voltage regulator tube is connected with the second node, and the circuit switch is connected with the first node.
Therefore, the series connection sequence of the second voltage-regulator tube and the switching element between the first node and the second node can be reasonably adjusted according to the use of different types of switching elements, and the switching elements are flexibly arranged.
In one possible approach, the switching element may be a relay, a contactor, a semiconductor switch connected in parallel with a diode, a metal-oxide-semiconductor field-effect transistor (MOSFET), or an Insulated Gate Bipolar Transistor (IGBT), wherein the semiconductor switch may be a MOSFET or a reverse conducting IGBT.
In a second aspect, the present application provides an inverter system, which specifically includes the voltage regulating circuit, the isolation power supply, the driving optocoupler and the inverter provided by the present application, wherein the output end of the isolation power supply is connected with a bus capacitor, two ends of the bus capacitor are respectively connected with the first node and the second node of the voltage regulating circuit, and the isolation power supply provides bus voltage through the bus capacitor. The input end of the driving optocoupler is connected with the first node and the second node, the output end of the driving optocoupler is connected with a switch tube of the inverter, the driving optocoupler is used for controlling the on-off of the switch tube, and the switch tube can be a MOSFET or an IGBT.
According to the inverter system provided by the above, the inverter system can be applied to a photovoltaic power generation system. When the inverter starts, because the open-circuit voltage of the photovoltaic power generation system is higher and the output power is smaller, the switching tube bears larger peak voltage, at the moment, the voltage regulating circuit of the inverter system can provide smaller driving voltage for the switching tube of the inverter through controlling the on-off state of the circuit switch, and the switching speed of the switching tube is reduced, so that the peak voltage born by the switching tube is reduced; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
Drawings
FIG. 1 is a block diagram of a present photovoltaic power generation system;
FIG. 2 is a graph of a voltage-current-power relationship of a current photovoltaic power generation system;
FIG. 3 is a schematic diagram of a DC/AC inverter;
fig. 4 is a schematic diagram of the driving timing of the inverter in H6 bridge topology;
FIG. 5 is a schematic diagram of the switching tube states and current directions of the H6 bridge topology at time t1-t 2;
FIG. 6 is a schematic diagram of the switching tube states and current directions of the H6 bridge topology at time t2-t 3;
fig. 7 is a schematic structural diagram of a voltage regulating circuit provided in the present application;
fig. 8 is a schematic structural diagram of a switching tube driving circuit provided in the present application;
fig. 9 is a schematic structural diagram of another switching tube driving circuit provided in the present application;
fig. 10 is a schematic structural diagram of an inverter system provided in the present application;
fig. 11 is a schematic structural diagram of another inverter system provided in the present application.
Detailed Description
Before describing the technical solution of the embodiment of the present application, first, a technical scenario of the embodiment of the present application is described with reference to the drawings.
Fig. 3 is a schematic diagram of a DC/AC inverter. At present, in a photovoltaic power generation system, a mainstream DC/AC inverter structure is an H6 bridge topology structure shown in fig. 3, a main loop of the structure is composed of 6 switching tubes connected in parallel with diodes, the switching tubes in the main loop provide bus voltage by a bus capacitor of a DC/DC isolation power supply, and the switching tubes are controlled to be closed and opened by driving an optical coupler, so that high-frequency Sinusoidal Pulse Width Modulation (SPWM) is implemented on the switching tubes, and direct current from the isolation power supply is modulated into alternating current and output to a power grid.
Referring to fig. 4, a driving timing diagram of an inverter in an H6 bridge topology is shown. As shown in fig. 4, at time t0-t4, the voltage of the power grid is positive in the direction from point E to point F in fig. 3, at this time, the drive optocoupler drives the switching tubes Q1a, Q2b, and Q3a to perform high-frequency modulation, Q3b is closed normally, and Q1b and Q2a are opened normally; at the time t4-t5, the voltage of the power grid is negative in the direction from point E to point F in fig. 3, at this time, the optocoupler is driven to drive the switching tubes Q1b, Q2a and Q3b to perform high-frequency modulation, Q3a is closed normally, and Q1a and Q2b are opened normally; therefore, direct current of the isolated power supply is modulated into alternating current synchronous with the phase of the power grid, and grid-connected power transmission of the photovoltaic power generation system is achieved.
Due to the parasitic inductance L1 in the inverter, when the switching device is closed or opened, the current flowing through the loop may generate a spike voltage under the action of the parasitic inductance L1. For example, referring to fig. 5 and fig. 6, switching tube states and current directions of an H6 bridge topology at times t1-t3 are shown, where fig. 5 is a switching tube state and current direction diagram of an H6 bridge topology at times t1-t2, and fig. 6 is a switching tube state and current direction diagram of an H6 bridge topology at times t2-t 3. As shown in fig. 5, at time t1-t2, Q3b is closed, Q1a and Q2b are opened, and Q3a is closed, at this time, Q3a, Q3b, parasitic inductance L1 and the grid form a current loop, and the current flows from Q3b to Q3a as shown by the arrow in fig. 5. As shown in fig. 6, at time t2-t3, Q3b is closed, Q1a, Q2b are closed, Q3a is opened to form a current dead zone, which prevents Q1a, Q3a, Q3b, Q2b from passing through, at this time, Q1a, Q2b, parasitic inductor L1 and the grid form a current loop, the current direction is as shown by the arrow in fig. 5, flowing from Q1 1 to Q2 1, wherein the current dead zone of Q3 1 is set to be on after being turned off, i.e. Q1 1, Q2 1 will start to be on after Q3 1 is reliably turned off, but after Q3 1 is turned off, the current existing in the diode connected in parallel with Q3 1 does not change direction and magnitude, the current still flows through Q3 1 and Q3 1 until Q1 1, Q2 1 is closed, therefore, the voltage of Q1 1 and Q2 1 is more quickly applied to the peak voltage of the closed or the peak voltage of the device when Q3 is opened and the peak voltage of Q3 1 is applied to both sides of the peak, the greater the voltage developed across parasitic inductance L1, the higher the spike voltage applied to Q3a, and the greater the loss to Q3 a.
The application provides a voltage regulating circuit.
Fig. 7 is a schematic structural diagram of a voltage regulating circuit provided in the present application.
As shown in fig. 7, the voltage regulating circuit includes: the circuit comprises a first voltage regulator tube Z1, a second voltage regulator tube Z2, a voltage regulator resistor R1, a circuit switch T1, a first capacitor C1 and a second capacitor C2. The first voltage regulator tube Z1 and the first capacitor C1 are connected in parallel between a first node A and a second node B; the voltage stabilizing resistor R1 and the second capacitor C2 are connected between the second node B and the third node C in parallel; the second voltage-regulator tube Z2 and the circuit switch T1 are connected in series between the first node A and the second node B, and a circuit formed by connecting the second voltage-regulator tube Z2 and the circuit switch T1 in series is connected with the first voltage-regulator tube Z1 in parallel; the voltage stabilizing value of the first voltage stabilizing tube Z1 is larger than that of the second voltage stabilizing tube Z2; the voltage between the first node a and the third node C is the bus voltage Vm.
As an alternative implementation, the second regulator tube Z2 is located at a side close to the first node a and connected to the first node a, and the circuit switch T1 is located at a side close to the second node B and connected to the second node B; or, as another alternative implementation, the second zener tube Z2 is located at a side close to the second node B and connected to the second node B, and the circuit switch T1 is located at a side close to the first node a and connected to the first node a. The connection mode of the second regulator tube Z2 and the circuit switch T1 connected in series between the first node a and the second node B is not specifically limited in the present application, and the designs and concepts of switching the second regulator tube Z2 into the voltage regulating circuit and isolating the second regulator tube Z2 from the voltage regulating circuit can be achieved by switching on and off the circuit switch T1 without exceeding the protection scope of the present application.
Further, the circuit switch T1 may specifically include a switching element and a switch control circuit for controlling the closing and opening of the switching element. The switching element includes, but is not limited to, a relay, a contactor, a semiconductor switch connected in parallel with a diode, a transistor, a metal-oxide-semiconductor field-effect transistor (MOSFET), or an Insulated Gate Bipolar Transistor (IGBT), and the like, and the semiconductor switch connected in parallel with a diode includes, but is not limited to, a MOSFET or an inverse conducting IGBT. The present application is not limited to the type of the switching element and the specific circuit structure of the switching control circuit used in the voltage regulating circuit, and those skilled in the art can select the possible combinations of the switching element and the switching control circuit according to the technical solutions and concepts of the present application, and the design and concepts that can be applied herein do not exceed the protection scope of the present application.
The working principle of the voltage regulating circuit provided by the present application is specifically described below with reference to fig. 8.
Fig. 8 is a schematic structural diagram of a switching tube driving circuit provided in the present application. The switching tube driving circuit applies a voltage regulating circuit shown in fig. 7 to regulate the driving voltage of the switching tube. As shown in fig. 8, when the regulator circuit is in use, the second node B is used for Ground (GND) to form a zero potential node. The first node a and the second node B are connected to both ends of a bus capacitor C0 of the isolated power supply, respectively, so that the voltage between the first node a and the third node C is equal to a bus voltage Vm.
Specifically, the first node a is connected to the positive voltage terminal of the bus capacitor C0, so that the bus voltage Vm is positive at the first node a with respect to the second node B, the value of the positive voltage + Vp is equal to the regulated voltage value of the first voltage regulator tube Z1 when the circuit switch T1 is switched off, the third node C is connected with the negative voltage end of the bus capacitor C0, so that the bus voltage Vm is negative relative to the second node B at the third node C, the negative voltage has a value of (+ Vp) -Vm, so that the regulator circuit divides the bus voltage Vm into a positive voltage + Vp and a negative voltage-Vs through the first regulator tube Z1 and the regulator resistor R1, the positive voltage + Vp and the negative voltage-Vs are used for providing driving voltage for the driving optocoupler, and the positive voltage + Vp is used for providing driving voltage for the switching tube Q0, so that the switching tube Q0 is driven by the driving optocoupler to realize a closing and opening process.
When the circuit switch T1 is turned off, the first voltage-regulator tube Z1 and the voltage-regulator resistor R1 participate in voltage division of the bus voltage Vm, when the circuit switch T1 is turned on, the second voltage-regulator tube Z2 is switched into the voltage-regulating circuit, the first voltage-regulator tube Z1 is bypassed, and at the moment, the second voltage-regulator tube Z2 and the voltage-regulator resistor R1 participate in voltage division of the bus voltage Vm. Because the voltage stabilizing value of the first voltage stabilizing tube Z1 is different from that of the second voltage stabilizing tube Z2, the positive voltage + Vp at the two ends of the voltage stabilizing resistor R1 is different under the two conditions of the disconnection and the connection of the circuit switch T1, and the voltage regulation of the driving voltage of the switch tube Q0 can be realized by directly regulating the positive voltage + Vp.
Specifically, when the circuit switch T1 is switched from the open state to the closed state, the second voltage regulator tube Z2 is switched into the voltage regulator circuit to bypass the first voltage regulator tube Z1, so that the positive voltage + Vp is reduced, that is, the driving voltage of the switch tube Q0 is reduced, and the switching speed of the switch tube Q0 is reduced; on the contrary, when the circuit switch T1 is switched from the closed state to the open state, the first regulator tube Z1 is switched into the regulator circuit, so that the positive voltage + Vp is increased, that is, the driving voltage of the switching tube Q0 is increased, and the switching speed of the switching tube Q0 is increased.
It should be added that, in this application, the regulated voltage value V2 of the second regulator tube Z2 needs to be greater than the conduction voltage of the switch tube Q0, so as to ensure that when the second regulator tube Z2 is switched into the voltage regulating circuit, the positive voltage + Vp of the voltage regulating circuit can drive the switch tube Q0 to conduct.
The working principle of the voltage regulating circuit provided in fig. 8 of the present application is further explained with reference to specific examples.
In one example, the bus voltage Vm of the DC/DC isolated power supply is 21V, the regulated value V1 of the first regulator tube Z1 is 16V, and the regulated value V2 of the second regulator tube Z2 is 10V, that is, the regulated value of the first regulator tube Z1 is greater than that of the second regulator tube Z2. When the circuit switch T1 is open, the positive voltage + Vp-V1-V (+16V), and when the circuit switch T1 is closed, the positive voltage + Vp-V2-V (+ 10V). Therefore, the driving voltage of the switching tube Q0 can be adjusted to 16V or 10V by opening or closing the control circuit switch T1, and the switching speed of the switching tube Q0 can be adjusted.
Therefore, the voltage regulating circuit can be applied to a photovoltaic power generation system and provides variable driving voltage for the switching tube in the inverter, when the inverter starts to start, the switching tube bears larger peak voltage due to higher open-circuit voltage and smaller output power of the photovoltaic power generation system, and at the moment, the switching tube can provide smaller driving voltage for the switching tube by controlling the on-off state of the circuit switch, so that the switching speed of the switching tube is reduced, and the peak voltage borne by the switching tube is reduced; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
Fig. 9 is a schematic structural diagram of another switching tube driving circuit provided in the present application.
As shown in fig. 9, the switching tube driving circuit structure is different from the structure shown in fig. 8 in that a first node a is connected to a negative voltage end of a bus capacitor C0, so that a bus voltage Vm is a negative voltage at the first node a with respect to a second node B, a value-Vs of the negative voltage is equal to a regulated value of a first regulator tube Z1 when a circuit switch T1 is turned off, a third node C is connected to a positive voltage end of a bus capacitor C0, so that the bus voltage Vm is a positive voltage at the third node C with respect to the second node B, a value + Vp of the positive voltage is Vm-Vs, and thus, the regulator circuit divides the bus voltage Vm into a negative voltage-Vs and a positive voltage + Vp through the first regulator tube Z1 and a regulator resistor R1, wherein the positive voltage + Vp and the negative voltage-Vs are used to provide a driving voltage for driving the driving of the driving transistor Q0, and the positive voltage + Vp is used to provide a driving voltage for the switching tube Q, the switching tube Q0 is driven by the driving optocoupler to realize the closing and opening processes.
When the circuit switch T1 is switched off, the first voltage-regulator tube Z1 and the voltage-regulator resistor R1 participate in voltage division of the bus voltage Vm, when the circuit switch T1 is switched off, the second voltage-regulator tube Z2 is switched into a voltage-regulating circuit, the first voltage-regulator tube Z1 is bypassed, and at the moment, the second voltage-regulator tube Z2 and the voltage-regulator resistor R1 participate in voltage division of the bus voltage Vm. Because the voltage stabilizing value of the first voltage stabilizing tube Z1 is different from that of the second voltage stabilizing tube Z2, the negative voltage-Vs is respectively distributed to different values under the two conditions of opening and closing of the circuit switch T1, and further the positive voltage + Vp at two ends of the voltage stabilizing resistor R1 is different, so that the positive voltage + Vp can be indirectly adjusted by adjusting the negative voltage-Vs, and the voltage regulation of the driving voltage of the switch tube Q0 is realized.
Specifically, when the circuit switch T1 is switched from an open state to a closed state, the second voltage regulator tube Z2 is switched into the voltage regulator circuit to bypass the first voltage regulator tube Z1, so that the positive voltage + Vp is increased, that is, the driving voltage of the switch tube Q0 is increased, and the switching speed of the switch tube Q0 is increased; in contrast, when the circuit switch T1 changes from the closed state to the open state, the positive voltage + Vp can be decreased, that is, the driving voltage of the switching tube Q0 is decreased, and the switching speed of the switching tube Q0 is decreased.
It should be added that, in the present application, the difference between the bus voltage Vm and the regulated voltage value of the first regulator tube Z1 needs to be greater than the conduction voltage of the switch tube Q0, so as to ensure that the positive voltage + Vp of the regulator circuit can drive the switch tube Q0 to conduct when the first regulator tube Z1 is switched into the regulator circuit.
The working principle of the voltage regulating circuit provided in fig. 9 of the present application is further explained with reference to specific examples.
In one example, the bus voltage Vm of the DC/DC isolated power supply is 21V, the regulated value V1 of the first regulator tube Z1 is 11V, and the regulated value V2 of the second regulator tube Z2 is 5V, that is, the regulated value of the first regulator tube Z1 is greater than that of the second regulator tube Z2; when the circuit switch T1 is open, the positive voltage + Vp-V1-V (+10V), and when the circuit switch T1 is closed, the positive voltage + Vp-V2-V (+ 16V). Therefore, the driving voltage of the switching tube Q0 can be adjusted to 10V or 16V by opening or closing the control circuit switch T1, and the switching speed of the switching tube Q0 can be adjusted.
Therefore, the voltage regulating circuit can be applied to a photovoltaic power generation system and provides variable driving voltage for the switching tube in the inverter, when the inverter starts to start, the switching tube bears larger peak voltage due to higher open-circuit voltage and smaller output power of the photovoltaic power generation system, and at the moment, the switching tube can provide smaller driving voltage for the switching tube by controlling the on-off state of the circuit switch, so that the switching speed of the switching tube is reduced, and the peak voltage borne by the switching tube is reduced; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
The present application further provides an inverter system.
The inverter system comprises the voltage regulating circuit, the isolation power supply, the driving optocoupler and the inverter.
The output end of the isolation power supply is connected with a bus capacitor, two ends of the bus capacitor are respectively connected with the first node and the third node of the voltage regulating circuit, and the isolation power supply is used for providing bus voltage through the bus capacitor. The input end of the driving optical coupler is connected with the first node and the third node, the output end of the driving optical coupler is connected with the switch tube of the inverter, and the driving optical coupler is used for controlling the on-off of the switch tube.
Fig. 10 is a schematic structural diagram of an inverter system provided in the present application.
As shown in fig. 10, in an embodiment, the voltage regulating circuit uses the structure shown in fig. 8 to regulate the driving voltage of the switching tube by directly regulating the positive voltage + Vp.
The bus capacitor C0 is connected with the isolation power output end, bus voltage Vm is provided through the bus capacitor C0, two ends of the bus capacitor C0 are respectively connected with a first node A and a third node C of the voltage regulating circuit, and the bus voltage Vm has positive voltage + Vp at the first node A and negative voltage-Vs at the third node C under the voltage division effect of the voltage regulating circuit. The input end of the driving optocoupler is connected with the first node A and the third node C, positive voltage + Vp and negative voltage-Vs are used for providing driving voltage, and the output end of the driving optocoupler is connected with a switching tube of the inverter and is used for providing positive voltage + Vp as the driving voltage of the switching tube.
As an alternative embodiment, the inverter system provided by the present application includes a DC/AC inverter with an H6 bridge topology as shown in fig. 3, and at this time, two driving optical couplers are provided for driving the switching tubes Q2a and Q2b, respectively.
The following description specifically explains an operation principle of the inverter system provided in fig. 10 in the application of the photovoltaic power generation system, with reference to a driving timing diagram of an H6 bridge topology shown in fig. 4 and a specific example.
When the inverter is started, because the open-circuit voltage of the photovoltaic power generation system is high, the switching tube can bear large peak voltage in the process of closing and opening the switching tube, and the loss of the switching tube is accelerated. According to the inverter system, the driving voltage of the switching tube is adjusted through the voltage adjusting circuit, so that the switching tube is driven by using smaller driving voltage when the inverter is started, the switching speed of the switching tube is reduced, and the peak voltage born by the switching tube is reduced; and after the load of the photovoltaic power generation system climbs, the driving voltage of the switching tube is increased through the voltage regulating circuit, so that the switching speed of the switching tube is increased, and the heat loss is reduced.
In one example, the bus voltage Vm of the isolated power supply is 21V, the regulated value V1 of the first regulator tube Z1 is 16V, and the regulated value V2 of the second regulator tube Z2 is 10V, that is, the regulated value of the first regulator tube Z1 is greater than that of the second regulator tube Z2. At the time of starting the inverter, for example, at T0, the circuit switch T1 is closed, the second regulator tube Z2 is cut into the regulator circuit, the first regulator tube Z1 is bypassed, and the positive voltage + Vp + V2 +10V is set in the regulator circuit, so that the optocoupler is driven to close the switch tube Q2b at the driving voltage of 10V, and the switch tube Q1a connected in series with the switch tube Q2b is closed, thereby forming a circuit as shown in fig. 5. Due to the fact that the driving voltage is low, the closing speed of the switching tube Q2b and the switching tube Q1a is low, the voltage generated by the parasitic inductor L1 is low, and therefore the peak voltage generated on the switching tube Q3a can be reduced.
Further, after the output power of the photovoltaic power generation system climbs, the output voltage of the photovoltaic power generation system is low, the current is large, the heat loss is increased when the switching tube adopts a slower switching speed, the influence of the peak voltage on the loss of the switching tube is reduced, and the main loss of the switching tube is the heat loss generated in the switching process. In order to reduce the heat loss of the switching tube, the circuit switch T1 may be opened, and the positive voltage + Vp of the voltage regulating circuit is made to be V1 to +16V, so that the optocoupler is driven to drive the switching tube to be closed or opened with a 16V driving voltage, thereby increasing the switching speed of the switching tube and reducing the heat loss.
Therefore, the inverter system provided by the application can be applied to a photovoltaic power generation system. When the inverter starts, because the open-circuit voltage of the photovoltaic power generation system is higher and the output power is smaller, the switching tube bears larger peak voltage, at the moment, the voltage regulating circuit of the inverter system can provide smaller driving voltage for the switching tube of the inverter through controlling the on-off state of the circuit switch, and the switching speed of the switching tube is reduced, so that the peak voltage born by the switching tube is reduced; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
Fig. 11 is a schematic structural diagram of another inverter system provided in the present application.
In another embodiment, as shown in fig. 11, the voltage regulating circuit uses the structure shown in fig. 9 to indirectly regulate the positive voltage + Vp by regulating the negative voltage-Vs, thereby realizing the voltage regulation of the driving voltage of the switching tube.
The inverter system shown in fig. 11 is structurally different from the inverter system shown in fig. 10 in that the bus capacitor C0 is connected to the first node a and the third node C of the voltage regulating circuit in the opposite direction, so that the bus voltage Vm has a negative voltage-Vs at the first node a and a positive voltage + Vp at the third node C under the voltage division of the voltage regulating circuit.
The following description specifically describes the operation principle of the inverter system provided in fig. 11 of the present application when applied to a photovoltaic power generation system, with reference to a driving timing diagram of an H6 bridge topology shown in fig. 4 and with reference to a specific example.
In one example, the bus voltage Vm of the DC/DC isolated power supply is 21V, the regulated value V1 of the first regulator tube Z1 is 11V, and the regulated value V2 of the second regulator tube Z2 is 5V. At the time T0, for example, when the inverter is started, the circuit switch T1 is opened, the second regulator tube Z1 is switched into the regulator circuit, and the positive voltage + Vp (+10V) of the regulator circuit is caused to drive the optocoupler to drive the switching tube Q2b to close at a driving voltage of 10V, so that the switching tube Q1a connected in series with the switching tube Q2b is closed, thereby forming a circuit as shown in fig. 5. Due to the fact that the driving voltage is low, the closing speed of the switching tube Q2b and the switching tube Q1a is low, the voltage generated by the parasitic inductor L1 is low, and therefore the peak voltage generated on the switching tube Q3a can be reduced.
Further, after the output power of the photovoltaic power generation system climbs, the output voltage of the photovoltaic power generation system is low, the current is large, the thermal loss is increased when the switching tube is switched at a slower switching speed, the influence of the peak voltage on the loss of the switching tube is reduced, and the main loss of the switching tube is the thermal loss generated in the switching process. Then, in order to reduce the heat loss of the switching tube, the circuit switch T1 may be closed, and the first voltage regulator Z1 may be bypassed, so that the positive voltage + Vp of the voltage regulator circuit is (+16V), thereby driving the optocoupler to drive the switching tube to be closed or opened with a driving voltage of 16V, so as to increase the switching speed of the switching tube and reduce the heat loss.
Therefore, the inverter system provided by the application can be applied to a photovoltaic power generation system. When the inverter starts, because the open-circuit voltage of the photovoltaic power generation system is higher and the output power is smaller, the switching tube bears larger peak voltage, at the moment, the voltage regulating circuit of the inverter system can provide smaller driving voltage for the switching tube of the inverter through controlling the on-off state of the circuit switch, and the switching speed of the switching tube is reduced, so that the peak voltage born by the switching tube is reduced; when the output power of the photovoltaic power generation system rises, the output voltage of the photovoltaic power generation system is low, the current is high, the heat loss is increased when the switching tube adopts a slower switching speed, and at the moment, a larger driving voltage can be provided for the switching tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switching tube and reduce the heat loss.
Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the application and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the application being indicated by the following claims.
It will be understood that the present application is not limited to the precise arrangements described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (8)
1. The utility model provides a voltage regulating circuit, its characterized in that is applied to photovoltaic power generation system, provides changeable driving voltage for the switch tube in the system's dc-to-ac converter, photovoltaic power generation system include the dc-to-ac converter, keep apart power, drive opto-coupler and voltage regulating circuit, voltage regulating circuit includes: the circuit comprises a first voltage-regulator tube, a second voltage-regulator tube, a voltage-regulator resistor, a circuit switch, a first capacitor and a second capacitor;
the first voltage regulator tube and the first capacitor are connected between a first node and a second node in parallel;
the voltage-stabilizing resistor and the second capacitor are connected in parallel between the second node and a third node;
the second voltage-regulator tube and the circuit switch are connected in series between the first node and the second node, and a circuit formed by connecting the second voltage-regulator tube and the circuit switch in series is connected with the first voltage-regulator tube in parallel;
the second voltage regulator tube is connected with the first node, and the circuit switch is connected with the second node; or, the second voltage regulator tube is connected with the second node, and the circuit switch is connected with the first node;
the voltage stabilizing value of the first voltage stabilizing tube is greater than that of the second voltage stabilizing tube, and the voltage stabilizing value of the second voltage stabilizing tube is greater than the breakover voltage of the switch tube;
the first node and the third node are connected with the isolated power supply, the voltage between the first node and the third node is the bus voltage of the isolated power supply, and the second node is used for grounding;
the first node and the third node are connected with the input end of the driving optocoupler and used for taking the divided voltage of the bus voltage at the first node and the divided voltage of the bus voltage at the third node as the driving voltage of the driving optocoupler;
the output end of the driving optocoupler and the second node are connected with the switch tube; when the inverter starts to be started, the voltage regulating circuit provides smaller driving voltage for the switching tube by controlling the on-off state of the circuit switch so as to slow down the switching speed of the switching tube; when the output power of the photovoltaic power generation system climbs, the voltage regulating circuit provides larger driving voltage for the switch tube by controlling the on-off state of the circuit switch so as to accelerate the switching speed of the switch tube.
2. The voltage regulator circuit according to claim 1, wherein the circuit switch includes a switching element and a switch control circuit for controlling the switching element to be closed and opened.
3. The voltage regulator circuit according to claim 1, wherein the second node is a zero potential node, the bus voltage is a positive voltage at the first node relative to the second node, and the bus voltage is a negative voltage at the third node relative to the second node.
4. The voltage regulator circuit according to claim 1, wherein the second node is a zero potential node, the bus voltage is a negative voltage at the first node relative to the second node, and the bus voltage is a positive voltage at the third node relative to the second node.
5. The voltage regulation circuit of claim 2, wherein the switching element is a relay, a contactor, a semiconductor switch connected in parallel with a diode.
6. The voltage regulator circuit according to claim 5, wherein the semiconductor switch is a MOSFET or a reverse conducting IGBT.
7. An inverter system, comprising: the voltage regulation circuit, isolated power supply, drive optocoupler, and inverter of any of claims 1-6;
the output end of the isolation power supply is connected with a bus capacitor, two ends of the bus capacitor are respectively connected with the first node and the third node of the voltage regulating circuit, and the isolation power supply provides bus voltage through the bus capacitor;
the input end of the driving optocoupler is connected with the first node and the third node, the output end of the driving optocoupler is connected with a switch tube of the inverter, and the driving optocoupler is used for controlling the switch tube to be closed and opened.
8. The inverter system of claim 7, wherein the switching tubes are MOSFETs or IGBTs.
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| CN201811619706.0A CN109728739B (en) | 2018-12-28 | 2018-12-28 | Voltage regulating circuit and inverter system |
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| CN201811619706.0A CN109728739B (en) | 2018-12-28 | 2018-12-28 | Voltage regulating circuit and inverter system |
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