CN102624025A - A composite unit cascaded multi-level inverter circuit energy feedback device and its control method - Google Patents

Abstract

The invention relates to an energy feedback device with a composite unit cascade multi-level inverter circuit and a control method of the energy feedback device. The energy feedback device consists of a power unit based on a three-phase control rectifying circuit and a power unit based on a three-phase PWM (pulse width modulation) rectifying circuit, wherein the two power units are in cascade connection. Direct-current voltage of an intermediate direct-voltage circuit of the power unit based on the three-phase control rectifying circuit is stabilized within a safety range by controlling a closed loop of the direct-current voltage of the intermediate direct-voltage circuit of the power unit based on the three-phase control rectifying circuit in a feedback manner, while load feedback energy mainly flows into the intermediate direct-voltage circuit in the power unit based on the three-phase PWM rectifying circuit and is fed into the power grid in a grid integration inverter mode by the three-phase PWM rectifying circuit. The energy feedback device is capable of realizing feedback of load energy to the power grid, so that energy-saving effect is achieved, output voltage is stabilized, and meanwhile, the topological structure of the power units and complexity of control links are simplified to some extent. Further, usage number of insulated gate bi-polar transistors is reduced, manufacturing cost is reduced as well, and the energy feedback device has high economic value.

Description

A composite unit cascaded multi-level inverter circuit energy feedback device and its control method

technical field

The invention relates to an energy feedback device and a method thereof, in particular to a composite unit cascaded multi-level inverter circuit, an energy feedback device and a method thereof.

Background technique

With the development of power electronics technology, as one of the main achievements of the development of power electronics technology, high-voltage frequency converters are widely used in various fields of the national economy, such as metallurgy, due to their advantages such as high power factor, high efficiency, high precision, and wide speed range. , Mining, petrochemical, electric power and other industries have been widely used and are playing an increasingly important role.

At present, most of the general-purpose high-voltage inverters on the market are single-quadrant inverters, and their main circuit topology mostly uses power units based on uncontrolled rectification circuits or phase-controlled rectification circuits to form a cascaded multi-level inverter circuit structure. The circuit topology diagram of the high-voltage inverter is shown in Figure 1, the power unit based on the uncontrolled rectification circuit is shown in Figure 2, and the power unit based on the phase-controlled rectification circuit is shown in Figure 3. These traditional cascaded high-voltage frequency converters cannot be directly used in speed control systems that require four-quadrant operation of the motor, fast start-up and braking, and frequent forward and reverse rotation, such as high-speed elevators, mining hoists, rolling mills, large-scale planers, Winding mechanism tension system and machine tool spindle drive system, etc. When the motor decelerates, brakes, or lowers a heavy load with potential energy, the motor is in the state of regenerative power generation. Since the energy transmission of the uncontrolled and phase-controlled rectification circuit is irreversible, the generated regenerative power is transmitted to the filter capacitor on the DC side, resulting in high If the pumping voltage is not released in time, it will inevitably cause the overvoltage protection action of the inverter or cause overvoltage damage to the high-power components of the main circuit. In engineering, this kind of pumping energy is mostly consumed as heat energy or other forms, which greatly wastes energy and does not meet the current energy-saving needs.

The PWM rectifier circuit has the advantages of fast dynamic response and adjustable DC side voltage range, which can meet the performance requirements of bidirectional flow of cascaded multi-level energy. Using the PWM rectifier in the power unit of the high-voltage frequency converter can realize the unit power factor rectification operation. Therefore, the phase-shifting transformer that realizes multiple rectification in the high-voltage frequency converter can be replaced by an ordinary power frequency transformer, which can save complex shifting Phase wiring. However, the PWM rectifier control circuit needs to detect the amount of information such as the AC side current and the DC side voltage to implement the PWM rectification control algorithm. The cost of the detection and control link increases, and at the same time makes the control of the system very complicated, which also affects the reliability of the system. adverse effects.

Contents of the invention

The present invention mainly solves the technical problems existing in the prior art; it provides a method that can realize load energy feedback to the power grid to achieve energy-saving effects, and at the same time maintain a stable output voltage value, which can not only meet the requirements of the four-quadrant operation of the motor, but also A composite unit cascaded multi-level inverter circuit, an energy feedback device and a method thereof simplify the design requirements of a phase-shifting transformer.

Another purpose of the present invention is to solve the technical problems existing in the prior art; to provide a power unit system topology structure and the complexity of the control links are simplified, and the number of insulated gate bipolar transistors used is reduced, thereby reducing the cost Cost, a composite unit cascaded multi-level inverter circuit, an energy feedback device and a method thereof with high economic value.

Above-mentioned technical problem of the present invention is mainly solved by following technical scheme:

A composite unit cascaded multi-level inverter circuit and an energy feedback device, characterized in that it includes two cascaded energy feedback units, and several power units cascaded sequentially between the energy feedback units, the power The units are cascaded with the energy feedback unit.

Cascaded multi-level inverter circuits and energy feedback devices in the above composite unit, the energy feedback unit includes energy feedback unit A1 and energy feedback unit A4; the power unit is two, respectively power unit A2 and power unit A3.

A composite unit cascaded multi-level inverter circuit and an energy feedback device, characterized in that it includes two cascaded power units and a number of energy feedback units cascaded sequentially between the power units, the power unit Both are cascaded with the energy feedback unit.

Cascaded multilevel inverter circuits and energy feedback devices in the above-mentioned composite unit, the power unit includes a power unit A5 and a power unit A10; there are four energy feedback units, which are respectively energy feedback unit A6 and energy feedback unit A7, energy feedback unit A8, energy feedback unit A9.

Cascaded multi-level inverter circuits and energy feedback devices in the above-mentioned compound unit, the energy feedback unit includes a power unit based on a three-phase PWM rectifier circuit, and the power unit based on a three-phase PWM rectifier circuit is composed of an inverter circuit , an intermediate direct voltage circuit and a three-phase PWM rectifier circuit in parallel, the inverter circuit is a single-phase H-type bridge circuit composed of insulated gate bipolar transistors; the intermediate direct voltage circuit is a DC capacitor; The three-phase PWM rectifier circuit is composed of insulated gate bipolar transistors T1, T2, T3, T4, T5, T6. The insulated gate bipolar transistors T1, T3, and T5 have a common collector, and their emitters are respectively connected to the three-phase power supply. The three phases are connected, the insulated gate bipolar transistors T4, T6, and T2 have a common emitter, and their collectors are respectively connected to the three phases of the three-phase power supply.

In the above composite unit cascaded multi-level inverter circuit and energy feedback device, the power unit includes a power unit based on a three-phase phase-controlled rectifier circuit, and the power unit based on a three-phase phase-controlled rectifier circuit is controlled by an inverter circuit, an intermediate direct voltage circuit and a three-phase phase-controlled rectifier circuit in parallel, the inverter circuit is a single-phase H-type bridge circuit composed of insulated gate bipolar transistors; the intermediate direct voltage circuit is a DC capacitor ; The three-phase phase-controlled rectifier circuit is composed of thyristors VT1, VT2, VT3, VT4, VT5, VT6, the thyristors VT1, VT3, VT5 have a common cathode, and their anodes are respectively connected with the three phases of the three-phase power supply, and the thyristors VT4, VT6 , VT2 common anode, its cathode is respectively connected with the three phases of the three-phase power supply.

A composite unit cascaded multi-level inverter circuit and an energy feedback method, characterized in that it includes the following two selection steps:

Select step 1, when the voltage of capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PMW control signal to control the insulated gate bipolar transistor S9a, S8a is turned on and the insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows into the antiparallel diode and insulated gate bipolar transistor S9a through the output port a1 of the inverter circuit of the power unit A3 The anti-parallel diode of the transistor S8a charges the capacitor C1, then flows out from the output port b1 of the inverter circuit of the power unit A1, and finally flows in from the output port a2 of the inverter circuit of the power unit A4, and passes through the inverter of the insulated gate bipolar transistor S9b The parallel diode, the intermediate direct voltage circuit capacitor C2 and the anti-parallel diode of the insulated gate bipolar transistor S8b and the output port b2 of the inverter circuit of the power unit A4 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A2;

Select step 2, when the voltage of the capacitor C1 is stabilized to Vcon, the controller sends a PMW control signal to control the conduction of the IGBT S7a and the IGBTs S8a, S9a, and S10a in the inverter circuit of the power unit A3 All are turned off, so that the load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A3, and then outputs from the inverter circuit of the power unit A3 Port b1 flows out, and finally flows in from the output port a2 of the inverter circuit of the power unit A4, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate direct voltage circuit, and the antiparallel diode of the insulated gate bipolar transistor S8b and The loop of the output port b2 of the inverter circuit of the power unit A4 directly flows into the intermediate DC circuit capacitor C2 of the power unit A4.

A composite unit cascaded multi-level inverter circuit and an energy feedback method, including the selection steps of the following two situations:

Select step 1, when the voltage of capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PMW control signal to control the insulated gate bipolar transistor S9a, S8a is turned on and the insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows into the antiparallel diode and insulated gate bipolar transistor S9a through the output port a1 of the inverter circuit of the power unit A5 The anti-parallel diode of the transistor S8a charges the capacitor C1, then flows out from the output port b1 of the inverter circuit of the power unit A5, and finally flows in from the output port a2 of the inverter circuit of the power unit A6, and passes through the inverter of the insulated gate bipolar transistor S9b The parallel diode, the intermediate direct voltage circuit capacitor C2 and the anti-parallel diode of the insulated gate bipolar transistor S8b and the output port b2 of the inverter circuit of the power unit A6 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A6;

Select step 2, when the voltage of the capacitor C1 is stable to Vcon, the controller sends a PMW control signal to control the conduction of the IGBT S7a and the IGBTs S8a, S9a, and S10a in the inverter circuit of the power unit A5 All are turned off, so that the load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A5, and then outputs from the inverter circuit of the power unit A5 Port b1 flows out, and finally flows in from the output port a2 of the inverter circuit of the power unit A6, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate direct voltage circuit, and the antiparallel diode of the insulated gate bipolar transistor S8b and The loop of the output port b2 of the inverter circuit of the power unit A6 directly flows into the intermediate DC circuit capacitor C2 of the power unit A6.

Therefore, the present invention has the following advantages: 1, the circuit of the present invention cascades the power unit based on the three-phase PWM rectifier circuit and the power unit based on the three-phase phase-controlled rectifier circuit, and cascades with the power unit based on the three-phase phase-controlled rectifier circuit Compared with the multi-level inverter circuit, the circuit of the present invention can realize the feedback of load energy to the power grid to achieve the effect of energy saving, and at the same time maintain a stable output voltage value. Using the circuit of the present invention for a high-voltage frequency converter can not only meet the requirements of four-quadrant operation of the motor , can also simplify the design requirements of the phase-shifting transformer; 2. Compared with the power unit cascaded multi-level inverter circuit based on the three-phase PWM rectifier circuit, the circuit of the present invention simplifies the power unit system topology to a certain extent The complexity of the control link and the number of insulated gate bipolar transistors are reduced, thereby reducing the manufacturing cost and having high economic value.

Description of drawings

Figure 1 is a topology diagram of a traditional cascaded high-voltage inverter.

Fig. 2 is a main circuit diagram of a power unit based on a three-phase uncontrolled rectifier circuit.

Fig. 3 is a main circuit diagram of a power unit based on a three-phase phase-controlled rectifier circuit.

Fig. 4 is a main circuit diagram of a power unit based on a three-phase PWM rectifier circuit.

Fig. 5(a) is a specific circuit structure diagram of the cascaded multi-level inverter circuit in the embodiment of the present invention.

Fig. 5(b) is another specific circuit structure diagram of the cascaded multi-level inverter circuit in the embodiment of the present invention.

Figure 6(a) is a schematic diagram of a cascaded multi-level inverter circuit using a traditional control method.

FIG. 6( b ) is a schematic diagram of the control method when the voltage of the capacitor C1 is lower than Vcon in FIG. 5( a ).

FIG. 6( c ) is a schematic diagram of the control method when the voltage of the capacitor C1 is stabilized at Vcon in FIG. 5( a ).

FIG. 6( d ) is a schematic diagram of the control method when the voltage of the capacitor C1 is lower than Vcon in FIG. 5( b ).

FIG. 6( e ) is a schematic diagram of the control method when the voltage of the capacitor C1 is stabilized at Vcon in FIG. 5( b ).

Detailed ways

The technical solutions of the present invention will be further specifically described below through the embodiments and in conjunction with the accompanying drawings.

Example:

The present invention will be further elaborated below in conjunction with the accompanying drawings and specific implementation.

Figure 1 is a topology diagram of a traditional cascaded high-voltage inverter. The traditional cascaded high-voltage inverter is composed of a phase-shifting transformer, a power unit, and a controller. The three-phase power units TA1, TA2, TA3, TA4, TB1, TB2, TB3, TB4, TC1, TC2, TC3, and TC4 provide three-phase power supply, and the output voltage of each power unit is cascaded and superimposed to form a three-phase sine wave , to supply power to the motor load.

The power unit in the prior art includes a power unit based on a three-phase phase-controlled rectifier circuit and a power unit based on a three-phase PWM rectifier circuit, as shown in Figure 3 and Figure 4 respectively, the power unit based on a three-phase phase-controlled rectifier circuit and the power unit based on a three-phase PWM rectifier circuit The power unit based on the three-phase PWM rectifier circuit is composed of a rectifier circuit, an intermediate DC circuit and an inverter circuit connected in parallel.

The rectifier circuit in the power unit based on the three-phase phase-controlled rectifier circuit is composed of thyristors. Figure 3 shows a specific implementation of the power unit based on the three-phase phase-controlled rectifier circuit. The inverter circuit uses four insulated gate bipolar Type transistors constitute a single-phase H-type bridge circuit; the intermediate direct voltage circuit is a DC capacitor; the rectifier circuit is a three-phase phase-controlled rectifier circuit composed of thyristors VT1, VT2, VT3, VT4, VT5, VT6, thyristors VT1, VT3, VT5 has a common cathode, and its anodes are respectively connected to the three phases of the three-phase power supply. Thyristors VT4, VT6, and VT2 have common anodes, and their cathodes are respectively connected to the three phases of the three-phase power supply. In the power unit based on the three-phase phase-controlled rectifier circuit, the capacitor voltage of the intermediate DC circuit and the output voltage signal of the inverter circuit are sent to the controller, processed by the controller, and then the output signal of the controller controls the insulation barrier in the inverter circuit. Bipolar transistors, so as to realize the energy transmission of the input power supply to the load, but cannot realize the load energy feedback control.

Specifically, in the high-voltage inverter, the secondary side of the phase-shifting transformer is connected to each power unit TA1, TA2, TA3, TA4, TB1, TB2, TB3, TB4, TC1, TC2, TC3, TC4 through filter reactors respectively , a phase-shifting transformer corresponds to a power unit, the input side of the power unit is a three-phase phase-controlled rectifier circuit, the intermediate DC circuit is a DC charging part composed of DC capacitors, and the output side is an inverter circuit. The multi-level inverter circuit formed by cascading power units is connected to the controller. The motor speed and voltage signals are sent to the controller through the power unit. After being processed by the controller, the output signal controls the four insulated gate bipolar inverter circuits. The transistor is turned on and off, so that the inverter circuit outputs a voltage waveform with corresponding amplitude and frequency.

When the motor is working in the electric state, the AC power input to the power unit becomes DC power after passing through the three-phase phase-controlled rectification circuit, which is added to the capacitor of the intermediate DC circuit, and then controlled by the controller to control the four insulation barriers in the inverter circuit The bipolar transistors Q1~Q4 make the DC power become AC power with a certain voltage amplitude and frequency again. The output voltages of the inverter circuits of each power unit are cascaded and stacked to form the three-phase sine wave AC power required by the motor, which is used to drive the motor. At this time, the electric energy is delivered to the motor by the cascaded multi-level inverter circuit formed by cascading power units from the input power supply, and the motor runs in the first and third quadrants. The three-phase phase-controlled rectification circuit of the transformer circuit has been working in the rectification state.

When the motor works in the braking state, since the thyristor cannot be turned on in reverse, the energy generated by the braking operation of the motor is quickly fed back to the intermediate DC circuit through the rectification circuit composed of the anti-parallel diode of the insulated gate bipolar transistor in the inverter circuit. On the capacitor, a pump voltage is generated. This energy can use a three-phase PWM rectifier circuit to realize bidirectional flow of energy and feed energy back to the grid.

The rectifier circuit in the power unit based on the three-phase PWM rectifier circuit is composed of insulated gate bipolar transistors. As shown in Figure 4, it is a specific implementation of the power unit based on the three-phase PWM rectifier circuit. The inverter circuit uses four isolated The gate bipolar transistors constitute a single-phase H-type bridge circuit; the intermediate direct voltage circuit is a DC capacitor; the three-phase PWM rectifier circuit is composed of insulated gate bipolar transistors T1, T2, T3, T4, T5, T6, and the insulated gate Bipolar transistors T1, T3, and T5 have common collectors, and their emitters are respectively connected to the three phases of the three-phase power supply. Insulated gate bipolar transistors T4, T6, and T2 have common emitters, and their collectors are respectively connected to the three-phase power supply. of three-phase connection.

In the power unit based on the three-phase PWM rectifier circuit, the input side current of the rectifier circuit, the DC capacitor voltage of the intermediate direct voltage circuit, and the output voltage signal of the inverter circuit are sent to the controller, processed by the controller, and then output by the controller at the same time Control the insulated gate bipolar transistors in the rectifier circuit and the inverter circuit, so as to realize the bidirectional flow of energy, which can realize the energy transmission of the input power supply to the load, and can also realize the load energy feedback control. Specifically, in the high-voltage inverter, the secondary side of the phase-shifting transformer is respectively connected to each power unit TA1, TA2, TA3, TA4, TB1, TB2, TB3, TB4, TC1, TC2, TC3, TC4 through the filter reactor The input side of the power unit is a three-phase PWM rectifier circuit composed of six insulated gate bipolar transistors T1~T6 connected in a three-phase bridge circuit, and the intermediate direct voltage circuit is a DC charging part composed of a DC capacitor , the output side is an inverter circuit. The multi-level inverter circuit formed by cascading power units is connected to the controller. The capacitor voltage of the intermediate DC circuit and the current signal of the input side of the power unit are sent to the controller. After being processed by the controller, the control signal is output to control the three The on-off of the six insulated gate bipolar transistors of the phase PWM rectifier circuit enables the three-phase PWM rectifier circuit to work both in the rectification state and in the inverter state, ensuring bidirectional flow control of energy; at the same time, the motor speed and After the voltage signal is sent to the controller, after being processed by the controller, the output signal controls the on-off of the four insulated gate bipolar transistors in the inverter circuit, so that the inverter circuit outputs a voltage waveform with a certain amplitude and frequency.

When the motor is working in the electric state, the controller controls the on-off of the six insulated gate bipolar transistors T1~T6 in the three-phase PWM rectifier circuit in the power unit, so that the power unit is in the rectification working state, and the AC power input to the power unit is passed through The three-phase PWM rectifier becomes DC power, which is added to the DC capacitor of the intermediate DC circuit, and then the controller controls the on-off of the four edge-gate bipolar transistors Q1~Q4 in the inverter circuit of the power unit to make the DC power AC power that becomes the desired voltage and frequency. The output voltages of the inverter circuits of each power unit are cascaded and stacked to form the three-phase sine wave AC power required by the motor, which is used to drive the motor. At this time, the electric energy is output to the motor from the power grid through the high-voltage frequency converter using the power unit cascaded multi-level inverter circuit, and the motor runs in the first and third quadrants.

When the motor works in the braking state, the energy generated by the motor's power generation operation is fed back to the capacitor of the intermediate DC circuit through the inverter circuit. When the capacitor voltage of the intermediate DC circuit exceeds the set value, control the on-off of the six insulated gate bipolar transistors T1~T6 in the three-phase PWM rectifier circuit, so that the three-phase PWM rectifier circuit in the power unit works in the inverter state , while controlling the frequency and phase of the output current of the three-phase PWM rectifier circuit, to ensure that the energy is fed back to the grid under the condition of unity power factor with the grid voltage. The energy generated by the motor generating operation is fed back into the power grid through the inverter circuit, the intermediate DC circuit, the three-phase PWM rectifier circuit and the filter reactor working in the inverter state, and the electric energy is passed by the motor through the cascaded multi-level inverter circuit. The high-voltage inverter of the structure flows into the power grid, and the motor works in the second and fourth quadrants. When the motor brakes and runs, the energy fed back by all cascaded units will be fed back to the grid through the three-phase PWM rectification circuit of the power unit.

The invention cascades the power unit based on the three-phase phase-controlled rectification circuit and the power unit based on the three-phase PWM rectification to form a new cascaded multi-level inverter circuit. Compared with the power unit cascaded multi-level inverter circuit completely based on the three-phase PWM rectifier circuit, the circuit of the present invention is simpler and more reliable in terms of circuit topology and control strategy. At the same time, the cascaded multilevel inverter circuit of the present invention adopts the power unit based on the three-phase phase-controlled rectifier circuit and the power unit based on the three-phase PWM rectifier circuit. The method still refers to the traditional power unit cascading method based on the three-phase uncontrolled rectifier circuit, and its connection with the phase-shifting transformer is still connected at a certain phase-shifting angle for the purpose of reducing input current harmonics, while based on the three-phase PWM The power unit cascading method of the rectifier circuit does not have this restriction because it does not require a phase shift of the transformer.

Figure 5(a) and Figure 5(b) are two specific implementations of the cascaded multilevel inverter circuit of the present invention. In the cascaded multi-level inverter circuit shown in Figure 5(a), power units A1 and A4 are based on three-phase PWM rectifier circuits, and the rest are based on phase-controlled rectifier circuits. The specific cascading mode of the power units is: the output terminal a1 of the inverter circuit of the A1 power unit is connected to the load, the output terminal b1 of the inverter circuit is connected to the output terminal a2 of the inverter circuit of the A2 power unit, and the output terminal a2 of the inverter circuit of the A2 power unit The terminal b2 is connected to the output terminal a3 of the inverter circuit of the A3 power unit, and the output terminal b3 of the inverter circuit of the A3 power unit is connected to the output terminal a4 of the inverter circuit of the A4 power unit, and finally the output terminal b4 of the inverter circuit of the A4 power unit is connected to Load connection; in the cascaded multi-level inverter circuit shown in Figure 5(b), power units A6, A7, A8, and A9 use power units based on three-phase PWM rectifier circuits, and the rest are based on phase-controlled rectifier circuits The power unit, the specific cascading mode of the power unit is the same as that in Fig. 5(a). During energy feedback, only part of the three-phase PWM rectifier circuit in the power unit needs to work in the inverter state to feed back the load energy into the grid. Therefore, some power units based on the three-phase PWM rectifier circuit can be used according to the load braking operation characteristics. Realize energy two-way control.

Since only part of the power units in the cascaded multi-level inverter circuit of the present invention use three-phase PWM rectifier circuits, compared with all power units using three-phase PWM rectifier circuits, the topology of the power unit system is simplified to a certain extent and the complexity of the control link, and reduce the number of insulated gate bipolar transistors used to achieve the purpose of saving costs; compared with all power units using phase-controlled rectification circuits, the design requirements for phase-shifting transformers are more stringent Simplified, the load energy can be fed into the grid, and it can also meet the harmonic suppression requirements of the AC side input current.

Figure 6 is a schematic diagram of the control method of the cascaded multi-level inverter circuit, and Figure 6(a) is a schematic diagram of the traditional control method for the cascaded multi-level inverter circuit, taking the load feedback current in the AC positive half cycle as an example , which flows in through the output port a1 of the inverter circuit of the power unit, through the anti-parallel diode of the insulated gate bipolar transistor S9a, the capacitor C1 of the intermediate DC circuit and the anti-parallel diode of the insulated gate bipolar transistor S8a, from the power unit The output port b1 of the inverter circuit flows out, and the output port a2 of the inverter circuit of the energy feedback unit flows in, passing through the anti-parallel connection of the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate direct voltage circuit and the anti-parallel connection of the insulated gate bipolar transistor S8b The diode flows out from the output port b2 of the inverter circuit of the energy feedback unit. This process completes the feedback of the load energy to the intermediate DC circuit capacitor of the power unit, but the load energy still cannot be fed back to the grid.

Figure 6(b) and (c) are schematic diagrams of the control method adopted in the circuit topology proposed in Figure 5(a) of the present invention. Also taking the load feedback current in the AC positive half cycle as an example, the present invention uses DC voltage closed-loop The control automatically controls the turn-on and turn-off of the insulated gate bipolar transistor in the inverter circuit of the power unit A3, so that the voltage of the capacitor C1 of the DC circuit is stabilized at a constant value Vcon, and the specific control is aimed at when the voltage of the capacitor C1 is lower than Vcon and When the voltage of capacitor C1 is stable to Vcon, there are two control processes:

When the voltage of the capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PWM control signal to control the insulated gate bipolar transistors S9a and S8a in the inverter circuit of the power unit A3 to turn on and The insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows through the antiparallel diode of the insulated gate bipolar transistor S9a and the antiparallel diode of the insulated gate bipolar transistor S8a through the output port a1 of the inverter circuit of the power unit A3. The diode is connected in parallel to charge the capacitor C1, and then flows out from the output port b1 of the inverter circuit of the power unit A3, and finally flows in from the output port a2 of the inverter circuit of the power unit A4, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the middle The direct voltage circuit capacitor C2 and the anti-parallel diode of the IGBT S8b and the output port b2 of the inverter circuit of the power unit A4 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A4, as shown in Figure 6(b) shown.

When the voltage of the capacitor C1 is stabilized to Vcon, the controller sends a PMW control signal to control the IGBT S7a in the inverter circuit of the power unit A3 to be turned on and the IGBTs S8a, S9a, and S10a to be all turned off. The load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A3, and then flows out from the output port b1 of the inverter circuit of the power unit A3, Finally, it flows from the output port a2 of the inverter circuit of the power unit A4, through the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate DC circuit, the anti-parallel diode of the insulated gate bipolar transistor S8b and the power unit A4 The loop of the output port b2 of the inverter circuit directly flows into the intermediate DC circuit capacitor C2 of the power unit A4, as shown in Fig. 6(c).

6(d) and 6(e) are schematic diagrams of the control method adopted in the circuit topology proposed in FIG. 5(b) of the present invention. The specific control has the following two control processes for when the voltage of capacitor C1 is lower than Vcon and when the voltage of capacitor C1 is stable at Vcon:

When the voltage of the capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PWM control signal to control the insulated gate bipolar transistors S9a and S8a in the inverter circuit of the power unit A5 to turn on and The insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows through the antiparallel diode of the insulated gate bipolar transistor S9a and the antiparallel diode of the insulated gate bipolar transistor S8a through the output port a1 of the inverter circuit of the power unit A5. The diode is connected in parallel to charge the capacitor C1, and then flows out from the output port b1 of the inverter circuit of the power unit A5, and finally flows in from the output port a2 of the inverter circuit of the power unit A6, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the middle The direct voltage circuit capacitor C2 and the anti-parallel diode of the IGBT S8b and the output port b2 of the inverter circuit of the power unit A6 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A6, as shown in Figure 6(d) shown.

When the voltage of the capacitor C1 is stabilized to Vcon, the controller sends a PMW control signal to control the IGBT S7a in the inverter circuit of the power unit A5 to be turned on and the IGBTs S8a, S9a, and S10a to be all turned off. The load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A5, and then flows out from the output port b1 of the inverter circuit of the power unit A5, Finally, it flows from the output port a2 of the inverter circuit of the power unit A6, through the antiparallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate DC circuit, the antiparallel diode of the insulated gate bipolar transistor S8b, and the power unit A6 The loop of the output port b2 of the inverter circuit directly flows into the intermediate DC circuit capacitor C2 of the power unit A6, as shown in Fig. 6(e).

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (8)

1. A composite unit cascaded multi-level inverter circuit and energy feedback device, characterized in that it comprises two cascaded energy feedback units and a number of power units cascaded sequentially between the energy feedback units, so The above power units are cascaded with the energy feedback unit. 2. The composite unit cascaded multi-level inverter circuit and energy feedback device according to claim 1, wherein the energy feedback unit comprises an energy feedback unit A1 and an energy feedback unit A4; the power unit is two They are power unit A2 and power unit A3 respectively. 3. A compound unit cascaded multi-level inverter circuit and an energy feedback device, characterized in that it comprises two cascaded power units and several energy feedback units arranged in sequence between the power units, said The power units are cascaded with the energy feedback unit. 4. The composite unit cascaded multi-level inverter circuit and energy feedback device according to claim 3, wherein the power unit includes a power unit A5 and a power unit A10; there are four energy feedback units, They are respectively energy feedback unit A6, energy feedback unit A7, energy feedback unit A8, and energy feedback unit A9. 5. The composite unit cascaded multi-level inverter circuit and energy feedback device according to claim 1 or 3, wherein the energy feedback unit includes a power unit based on a three-phase PWM rectifier circuit, and the based on The power unit of the three-phase PWM rectifier circuit is composed of an inverter circuit, an intermediate DC circuit and a three-phase PWM rectifier circuit connected in parallel, and the inverter circuits are all single-phase H-type bridge circuits composed of insulated gate bipolar transistors; The intermediate DC circuit is a DC capacitor; the three-phase PWM rectifier circuit is composed of insulated gate bipolar transistors T1, T2, T3, T4, T5, T6, insulated gate bipolar transistors T1, T3, T5 Collectors, the emitters of which are respectively connected to the three phases of the three-phase power supply, and the common emitters of the insulated gate bipolar transistors T4, T6, T2, and the collectors thereof are respectively connected to the three phases of the three-phase power supply. 6. The composite unit cascaded multi-level inverter circuit and energy feedback device according to claim 1 or 3, wherein the power unit includes a power unit based on a three-phase phase-controlled rectifier circuit, and the power unit based on The power unit of the three-phase phase-controlled rectifier circuit is composed of an inverter circuit, an intermediate DC circuit and a three-phase phase-controlled rectifier circuit connected in parallel, and the inverter circuit is a single-phase H-type bridge circuit composed of insulated gate bipolar transistors. ; The intermediate DC circuit is a DC capacitor; the three-phase phase-controlled rectifier circuit is composed of thyristors VT1, VT2, VT3, VT4, VT5, VT6, and the thyristors VT1, VT3, and VT5 have a common cathode, and their anodes are respectively connected to three The three phases of the three-phase power supply are connected, and the thyristors VT4, VT6, and VT2 have a common anode, and their cathodes are respectively connected to the three phases of the three-phase power supply. 7. A composite unit cascaded multi-level inverter circuit and energy feedback method according to claim 1, characterized in that, comprising the following two selection steps: Select step 1, when the voltage of the capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PMW control signal to control the insulated gate bipolar transistor S9a, S8a is turned on and the insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows into the antiparallel diode and insulated gate bipolar transistor S9a through the output port a1 of the inverter circuit of the power unit A3 The anti-parallel diode of the transistor S8a charges the capacitor C1, then flows out from the output port b1 of the inverter circuit of the power unit A3, and finally flows in from the output port a2 of the inverter circuit of the power unit A4, and passes through the inverter of the insulated gate bipolar transistor S9b The parallel diode, the intermediate direct voltage circuit capacitor C2 and the anti-parallel diode of the insulated gate bipolar transistor S8b and the output port b2 of the inverter circuit of the power unit A4 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A4; Select step 2, when the voltage of the capacitor C1 is stabilized to Vcon, the controller sends a PMW control signal to control the conduction of the IGBT S7a and the IGBTs S8a, S9a, and S10a in the inverter circuit of the power unit A3 All are turned off, so that the load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A3, and then outputs from the inverter circuit of the power unit A3 Port b1 flows out, and finally flows in from the output port a2 of the inverter circuit of the power unit A4, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate direct voltage circuit, and the antiparallel diode of the insulated gate bipolar transistor S8b and The loop of the output port b2 of the inverter circuit of the power unit A4 directly flows into the intermediate DC circuit capacitor C2 of the power unit A4. 8. A composite unit cascaded multi-level inverter circuit and energy feedback method according to claim 3, characterized in that it comprises the following two selection steps: Select step 1, when the voltage of capacitor C1 is lower than Vcon, the voltage detection unit detects the information and feeds it back to the controller, and the controller sends a PMW control signal to control the insulated gate bipolar transistor S9a, S8a is turned on and the insulated gate bipolar transistors S7a and S10a are turned off, so that the load feedback current flows into the antiparallel diode and insulated gate bipolar transistor S9a through the output port a1 of the inverter circuit of the power unit A5 The anti-parallel diode of the transistor S8a charges the capacitor C1, then flows out from the output port b1 of the inverter circuit of the power unit A5, and finally flows in from the output port a2 of the inverter circuit of the power unit A6, and passes through the inverter of the insulated gate bipolar transistor S9b The parallel diode, the intermediate direct voltage circuit capacitor C2 and the anti-parallel diode of the insulated gate bipolar transistor S8b and the output port b2 of the inverter circuit of the power unit A6 directly flow into the intermediate direct voltage circuit capacitor C2 of the power unit A6; Select step 2, when the voltage of the capacitor C1 is stable to Vcon, the controller sends a PMW control signal to control the conduction of the IGBT S7a and the IGBTs S8a, S9a, and S10a in the inverter circuit of the power unit A5 All are turned off, so that the load feedback current flows into the anti-parallel diode of the edge-gate bipolar transistor S9a and the insulated gate bipolar transistor S7a through the output port a1 of the inverter circuit of the power unit A5, and then outputs from the inverter circuit of the power unit A5 Port b1 flows out, and finally flows in from the output port a2 of the inverter circuit of the power unit A6, passing through the anti-parallel diode of the insulated gate bipolar transistor S9b, the capacitor C2 of the intermediate direct voltage circuit, and the antiparallel diode of the insulated gate bipolar transistor S8b and The loop of the output port b2 of the inverter circuit of the power unit A6 directly flows into the intermediate DC circuit capacitor C2 of the power unit A6.

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