CN101951011B - Solar photovoltaic and commercial power combined power supply system and control method thereof - Google Patents

Abstract

The invention discloses a solar photovoltaic and commercial power combined power supply system and a control method thereof, and belongs to the field of new energy power supply systems. The structure of the system comprises a photovoltaic array, a commercial power supply, a DC/DC converter, a PFC converter and a DC/AC inverter, wherein the photovoltaic array and the commercial power supply are connected with a direct current bus through the DC/DC converter and the PFC converter respectively and supply power to an alternating current load through the DC/AC inverter. In the invention, for fully utilizing solar, the DC/DC converter can operate with the maximum power of a photovoltaic battery; meanwhile, the commercial power is used as an auxiliary power supply, three power supply modes are realized, and the stable work of the load under various conditions is ensured.

Description

Control method of combined power supply system of solar photovoltaic and mains

technical field

The invention relates to a power supply system, in particular to a power supply system combined with a solar photovoltaic array and mains power and a power supply control method thereof, belonging to the field of new energy power supply systems. the

Background technique

With the continuous improvement of human living standards, the demand for energy has increased significantly. As a non-renewable energy source, fossil energy is becoming increasingly exhausted, and the environmental pollution it causes is becoming increasingly serious. As a green new energy power supply method, solar photovoltaic power supply has been more and more applied. Its biggest advantage is that it can be regenerated and has no pollution to the environment. the

The biggest characteristic of solar photovoltaic cells is that the external characteristic curve changes with light intensity and temperature. In order to maximize the use of solar energy, the DC converter is required to control the output of solar photovoltaic cells at all times to make it work near the maximum power point. the

The currently proposed solar power supply system cannot guarantee the continuous and stable operation of the load. Therefore, in order to fully use the solar energy and at the same time ensure that the load can work normally and stably at all times, an auxiliary power supply must be added to supply power to the load when the solar photovoltaic cannot meet the requirements. As a backup when needed. the

Contents of the invention

The object of the present invention is to propose a joint power supply system and its joint power supply control method with solar photovoltaic as the main power supply and mains power as the auxiliary power supply. the

The power supply system of the present invention includes a photovoltaic array, a mains power supply, a DC/DC converter, a PFC converter and a DC/AC inverter, wherein: the output of the photovoltaic array is connected to the DC bus through the DC/DC converter, and the mains power supply The output is connected to the DC bus through the PFC converter, the input of the DC/AC inverter is connected to the DC bus, and the output of the DC/AC inverter is connected to the load. the

The DC/DC converter is composed of a Boost circuit, a full-bridge converter and a rectification and filtering circuit connected in series in sequence. The input of the Boost circuit is connected to the output of the photovoltaic array, and the output of the rectification and filtering circuit is connected to the DC bus. the

The PFC converter is composed of a PFC rectifier circuit connected to a Boost PFC circuit, the input of the PFC rectifier circuit is connected to the output of the mains power supply, and the output of the Boost PFC circuit is connected to the DC bus. the

Based on the power supply control method of the power supply system of the present invention, the control circuit adopted by the control method is divided into two circuits, specifically:

The output current and voltage sampling of the photovoltaic array is connected to the MPPT controller, the output of the MPPT controller is connected to the adder, the output of the adder and the output current sampling of the photovoltaic array are connected to the first subtractor, and the output of the first subtractor passes through the first subtractor in turn. A current regulator, the first PWM circuit and the first gate drive circuit are connected to the Boost switching tube; the reference value of the voltage comparator and the output voltage sampling of the DC bus are connected to the second subtractor, and the output of the second subtractor is connected to the voltage regulator One output of the voltage regulator and the sinusoidal steamed bread wave are connected to the multiplier, the other output is connected to the adder through the blocking diode, the output of the multiplier and the PFC converter inductor current sampling are connected to the third subtractor, and the third subtraction The output of the converter passes through the second current regulator, the second PWM circuit and the second gate drive circuit in turn, and then connects to the Boost PFC switch tube;

The control method includes the following contents:

When the maximum output power of the photovoltaic array is greater than the power required by the load, the photovoltaic array supplies power to the load alone, and the DC bus voltage rises, making the output of the voltage regulator negative, and the duty cycle of the Boost PFC switch is 0. The blocking diode is turned on, and the output of the voltage regulator is used as an adjustment signal to reduce the given reference value of the voltage in the MPPT controller. At this time, the voltage regulator and the first current regulator form a double closed loop to stabilize the DC bus voltage. pressure state;

When the maximum output power of the photovoltaic array is less than the power required by the load, the photovoltaic array and the mains supply power to the load at the same time. At this time, the voltage regulator adjusts the duty cycle of the Boost PFC switch to control the DC bus voltage, and the blocking diode blocks , the two control circuits work independently, the maximum power point voltage value of the photovoltaic array calculated by the MPPT controller is used as the reference of the first current regulator, so that the photovoltaic array outputs the maximum power, and the insufficient power is provided by the mains power supply;

When the photovoltaic array fails to work, the DC/DC converter is turned off, and the load is supplied by the mains power supply. The voltage regulator adjusts the duty cycle of the Boost PFC switch tube to control the DC bus voltage to keep the DC bus voltage constant. the

The power supply system of the present invention uses the photovoltaic array as the main power supply, and controls the stable switching of the system in three modes according to the output power of the solar photovoltaic cells, that is, the solar single-channel independent work, the mains single-channel independent work, the solar/city The joint working mode of the two circuits of electricity realizes the use of solar energy as much as possible, and in the case of insufficient solar energy, the utility power is used as an auxiliary power supply to ensure that the load can continue to work stably. the

Description of drawings

Fig. 1 is a structural block diagram of the power supply system of the present invention. the

Fig. 2 is a schematic circuit diagram of the power supply system of the present invention. the

3 to 5 are respectively schematic diagrams of energy flow in three working modes of the power supply system of the present invention. the

Fig. 6 is a schematic structural diagram of the control circuit of the power supply system of the present invention. the

7 to 9 are respectively schematic diagrams of three working modes of the control circuit of the power supply system of the present invention. the

The main label names in the above drawings: PV is the photovoltaic array; V _g is the grid voltage (mains input voltage); C _in1 is the input filter capacitor; L _f1 , L _f2 , L _f3 , and L _f4 are all filter inductors; Q ₁ is the Boost switching tube; Q ₂ is the Boost PFC switching tube; T _r is the isolation transformer; R _ld is the load; V _o is the system output voltage; i _{pv_f} is the sampling of the output current of the photovoltaic array; v _{pv_f} is the sampling of the output voltage of the photovoltaic array; v _{o_f} is the DC bus output voltage sampling; i _{in2_f} is the PFC converter inductor current sampling; i _{in1_ref} and i _{in2_ref} are the reference values of the first and second current comparators respectively; Q _D1 is the driving signal of the Boost switch (Q ₁ ) ; Q _D2 is the driving signal of Boost PFC (Q ₂ ).

Detailed ways

The structure of the power supply system of the present invention is shown in Figure 1, including a photovoltaic array, a mains power supply, a DC/DC converter, a PFC (power factor correction) converter and a DC/AC inverter, wherein: the output of the photovoltaic array is passed through DC The /DC converter is connected to the DC bus, the output of the mains power is connected to the DC bus through the PFC converter, the input end of the DC/AC inverter is connected to the DC bus, and the output of the DC/AC inverter supplies power to the AC load. the

The specific circuit of the power supply system of the present invention is shown in FIG. 2 . The DC/DC converter is composed of Boost circuit 1, full bridge converter 2 and rectification filter circuit 3 connected in series; the PFC converter is composed of PFC rectifier circuit 4 connected to Boost PFC circuit 5; the DC/AC inverter is composed of The inverter circuit 6 is connected to the filter output circuit 7 to form. Among them: Boost circuit 1 is connected in parallel to the positive and negative output ends of the photovoltaic array PV; full-bridge converter 2 is a leading bridge arm composed of switching tubes Q _R1 and Q _R3 connected in series, and a lagging bridge arm composed of switching tubes Q _R2 and Q _R4 connected in series Composed in parallel, the two ends of the primary side of the isolation transformer T _r are respectively connected to the series nodes of the switching tubes of the leading and lagging two bridge arms, and the same-named terminal of the secondary side is connected to the two diodes D _B1 and D _B3 of the rectifying and filtering circuit 3 The series node of the diodes _DB2 and D _B4 is connected to each other, and the opposite end is connected to the series nodes of the other two diodes D _B2 and D _B4 ; The other two diodes D _B2 , D _B4 are connected in parallel in series, and the filter inductance L _f3 and filter capacitor C _f3 are connected in parallel with the diode series branch; the structure of the PFC rectifier circuit 4 is: two diodes D _B5 , D The series branch composed of _B7 in series is connected in parallel with the series branch composed of the other two diodes D _B6 and D _B8 connected in series; Boost PFC circuit 5 consists of filter inductor L _f2 , Boost PFC switch tube Q ₂ , freewheeling diode D ₂ , filter capacitor Composed _of C _f2 ; the inverter circuit 6 is composed of the leading bridge arm formed by the series connection of the switch tubes Q _R5 and Q _R7 and the parallel connection of the lagging bridge arm formed by the series connection of the switch tubes Q _R6 and Q _R8 ; The filter capacitor C _f4 and the load R _ld are composed. We use MOSFETs for the above switching tubes Q _R1 -Q _R8 , all of which have parasitic body diodes.

In order to make full use of solar energy and maximize the effectiveness of the photovoltaic array, the photovoltaic array must always work at the maximum power point, that is, the maximum power point tracking technology is required. There are many kinds of control algorithms for the current maximum power point tracking technology of solar cells, and the present invention adopts the method of perturbation and observation (Perturbation & Observation, P&O). the

According to the output power of the photovoltaic array and the size of the load, the energy flow of the three working modes of the power supply system of the present invention will be described in conjunction with FIGS. 3 to 5 . the

System working mode 1 [as shown in Figure 3]: the maximum output power of the photovoltaic array is greater than the power required by the load, and the DC/DC converter is controlled to work in a state of constant input voltage. The photovoltaic array alone provides the power required by the load, and the PFC converter Not working. the

System working mode 2 [as shown in Figure 4]: the maximum output power of the photovoltaic array is less than the power required by the load, and the DC/DC converter is controlled to work in the MPPT (Maximum Power Point Tracking, MPPT, maximum power point tracking) state, while the PFC The converter works, and the mains supply provides the remaining power required by the load. the

System working mode 3 [as shown in Figure 5]: The photovoltaic array cannot work normally, the DC/DC converter is turned off, the PFC converter works independently, and the power required by the load is provided by the mains alone. the

The purpose of the present invention is to maximize the use of solar energy while ensuring the normal operation of loads at all times, which requires energy management of the entire system. The control circuit structure of the power supply system of the present invention is shown in Figure 6, and the specific structure is as follows:

The photovoltaic array output current and voltage sampling i _{pv_f} and v _{pv_f} are connected to the MPPT controller, the output of the MPPT controller (the photovoltaic array maximum power point current i _{pv_m} ) is connected to the adder, and the output of the adder is connected to the photovoltaic array output current sampling i _{pv_f} The first subtractor is connected to the first subtractor, and the first subtractor sequentially passes through the first current regulator, the first PWM circuit and the first gate drive circuit to output the driving signal Q _D1 of the Boost switch tube _Q1 ; the voltage comparator reference value v _{o_ref} The output voltage sampling v _{o_f} of the DC bus is connected to the second subtractor, the output of the second subtractor is connected to the voltage regulator, one output of the voltage regulator and the sine wave are connected to the multiplier, and the other output passes through the blocking diode D _c is connected to the adder and grounded, the output of the multiplier and the PFC converter inductor current sampling i _{in2_f} are connected to the third subtractor, and the third subtractor passes through the second current regulator, the second PWM circuit and the second gate driver in sequence After the circuit, the drive signal Q _D2 of the Boost PFC switch tube Q ₂ is output.

The energy control method of this system will be described in detail below according to the working modes of the power supply system of the present invention and in conjunction with FIGS. 7 to 9 . the

The system works in mode 1 [as shown in Figure 7], that is, the maximum output power of the photovoltaic array is greater than the power required by the load, and the photovoltaic array supplies power to the load alone. If the voltage reference value v _{in1_ref} =v _{pv_m} in the MPPT controller is maintained, the photovoltaic array works at the maximum power point, and its output power is greater than the power required by the load, resulting in an increase in the DC bus voltage. At this time, the output of the voltage regulator is a negative value, so that the duty cycle of the Boost PFC switch _Q2 is 0, and at the same time, _Dc is turned on, and the output of the voltage regulator is used as an adjustment signal to reduce v _{in1_ref} , that is, reduce the solar energy The output current of the battery. At this time, the voltage regulator and the first current regulator form a double closed loop. The current loop is the inner loop, and the voltage loop is the outer loop. Adjust the duty cycle of the Boost switch tube _Q1 in the DC/DC converter to make the DC The bus voltage is stable.

The system works in mode 2 [as shown in Figure 8], that is, the maximum output power of the photovoltaic array is less than the power required by the load, and the photovoltaic array and the mains supply power to the load at the same time. At this time, the voltage regulator adjusts the duty ratio of the Boost PFC switch tube _Q2 to control the DC bus voltage, _Dc is blocked, and the two control circuits work independently. The maximum power point voltage value v _{pv_m} of the photovoltaic array calculated by the MPPT controller is used as a reference setting for the first current regulator, so that the photovoltaic array outputs the maximum power, and the insufficient power is provided by the mains.

The system works in mode 3 [as shown in Figure 9], that is, at night or in rainy weather, when the photovoltaic array cannot work, the DC/DC converter is turned off, and the power required by the load is provided by the mains. The voltage regulator adjusts the duty cycle of the Boost PFC switch tube Q ₂ to ensure a constant DC bus voltage.

The data of a specific embodiment of the present invention are as follows: photovoltaic array input voltage V _PV =28-37V; mains input DC voltage V _g =220VAC±20%; output DC bus voltage V _bus =380V; system output current (load current) I _o ＝5.3A; filter inductance L _f1 ＝90uH, L _f2 ＝300uH, L _f3 ＝290uH; transformer T _r primary-to-secondary ratio: 0.231; output filter capacitor C _f1 ＝220uF, C _f2 ＝560uF×3; MOSFET The switch tube Q ₁ adopts IPP111N15N3, Q ₂ adopts SPW47N60C3, Q _R1 , Q _R2 , Q _R3 , Q _R4 adopts FADP42AN15A; freewheeling diode D ₁ adopts V60200PG, D ₂ adopts _DSEI30-06A ; _B2 , _DB3 , _DB4 adopt STPSC806D; PFC rectifier diodes _DB5 , _DB6 , _DB7 , _DB8 adopt KBPC3508; switching frequency f _s =100kHz.

Claims (1)

1. the control method of a photovoltaic and civil power associating electric power system, it is characterized in that: this control method based on the structure of electric power system comprise photovoltaic array, mains supply, DC/DC converter, pfc converter and DC/AC inverter, wherein: the output of photovoltaic array is by DC/DC converter access dc bus, the output of mains supply accesses dc bus by pfc converter, the input of DC/AC inverter is connected into dc bus, and the output of DC/AC inverter connects load;

Described DC/DC converter is to be composed in series successively by Boost circuit (1), full-bridge converter (2) and current rectifying and wave filtering circuit (3), the input of Boost circuit (1) connects the output of photovoltaic array, the output access dc bus of current rectifying and wave filtering circuit (3) comprises a Boost switching tube (Q in the Boost circuit (1) ₁);

Described pfc converter connects BoostPFC circuit (5) by PFC rectification circuit (4) and forms, the input of PFC rectification circuit (4) connects the output of mains supply, the output access dc bus of Boost pfc circuit (5) comprises a Boost PFC switching tube (Q in the Boost pfc circuit (5) ₂);

The control circuit that this control method adopts is divided into two-way, is specially:

Photovoltaic array output current, voltage sample (i _{Pv_f}, v _{Pv_f}) access MPPT controller, the output access adder of MPPT controller, the output of adder and photovoltaic array output current sampling (i _{Pv_f}) access the first subtracter, the output of the first subtracter is successively by the first current regulator, the first pwm circuit be connected and connect Boost switching tube (Q behind the gate drive circuit ₁); Voltage comparator reference value (v _{O_ref}) and dc bus output voltage sampling (v _{O_f}) access the second subtracter, the output access voltage regulator of the second subtracter, one tunnel output of voltage regulator and sinusoidal steamed bun ripple access multiplier, another road output is by blocking diode (D _c) the access adder, the output of multiplier and pfc converter inductive current sampling (i _{In2_f}) access the 3rd subtracter, the output of the 3rd subtracter is successively by the second current regulator, the second pwm circuit be connected and connect Boost PFC switching tube (Q behind the gate drive circuit ₂);

This control method comprises following content:

When the peak power output of photovoltaic array during greater than the load power demand, powered to the load separately by photovoltaic array, DC bus-bar voltage raises, and it is negative that voltage regulator is output as, Boost PFC switching tube (Q ₂) duty ratio be 0, make simultaneously blocking diode (D _c) conducting, the output of voltage regulator makes voltage given reference value (v in the MPPT controller as adjusting signal _{In1_ref}) reduce, this moment, voltage regulator and the first current regulator formed two closed loops, made the dc bus voltage stabilizing, were in the voltage stabilizing state;

When the peak power output of photovoltaic array during less than the load power demand, powered to the load simultaneously by photovoltaic array and mains supply, this moment, voltage regulator was regulated Boost PFC switching tube (Q ₂) the Duty ratio control DC bus-bar voltage, blocking diode (D _c) blocking-up, the two-way control circuit works alone, the photovoltaic array maximum power point voltage value (v that the MPPT controller calculates _{Pv_m}) given as the benchmark of the first current regulator, making the photovoltaic array Maximum Power Output, deficit power is provided by mains supply;

When photovoltaic array can't be worked, close the DC/DC converter, powered to the load by mains supply, voltage regulator is regulated Boost PFC switching tube (Q ₂) the Duty ratio control DC bus-bar voltage, make DC bus-bar voltage constant.

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